|“||Since I just turned 16 a month ago, I wouldn’t mind getting my license. I can’t do that if I’m dead you know.||”|
— Erica to Derek in Battlefield
The days following his ascension to Alpha Werewolf status, Derek was recruiting and turning teenagers into Werewolves, particularly those who had problems such as loneliness and lack of strength and power. One day, he met Erica, an epileptic teenage girl that suffered from an enourmous case of epilepsy that made her a target of the abuse from her peers. Seeing her as a great candidate for his pack, Derek turned her into a Beta Werewolf, pledging that it would make her epilepsy vanish permanently, which Erica accepted right away, making her the third person Derek turned since becoming an Alpha overall but the second official member of his pack.
Erica, enjoying the power she gained from lycanthropy, shed her timid and self-conscious persona and became a much more beautiful, sexy and overconfident girl, developping close relationships with her new Alpha and packmates Isaac Lahey and Vernon Boyd. During her time as a Beta in the Hale Pack, Erica complied with Derek's orders without argument or question, even if his orders were to harm and/or kill someone, such as when he ordered her and Isaac to kill Lydia Martin when she was believed to be the Kanima. She also seemed to develop an attraction toward Derek but he wished her to go after Scott McCall instead to end his affair with Allison Argent.
Soon, the threats of the Kanima, who was eventually revealed to be Jackson Whittemore, and the growing number of Argent Hunters frightened Erica and Boyd so much that they made the difficult decision of leaving Beacon Hills and search for another pack elsewhere. Unfortunately, before they could make it out of their hometown, they were captured, first by Gerard Argent and his then-brainwashed granddaughter Allison, prior to being released by Chris Argent, and then again by the newly-arrived Alpha Pack, who intended to use the young Werewolves as leverage to convince Derek to join their pack, so Scott, who possessed the potential to become an exceptionally rare True Alpha, would be more willing to join them as well.
Given Erica and Boyd's lack of contact during summer and certain that they were captured by the Alpha Pack, Derek, Isaac and Peter searched for them for nearly four months but their searches yielded no positive results. Derek was intent in getting the two of them back that he went so far as to help Scott, Stiles and Alan Deaton give Isaac a cold bath so he would remember the place where he found the Alpha Pack holding Erica and Boyd. Through this method, Isaac revealed that Boyd was alive and locked in the vault of First National Bank with another unknown female Werewolf; Erica, on the other hand, had been killed by the Alphas, with Isaac recalling the moment he was locked in a closet and found her dead body inside there when the Alphas caught him breaking into the bank. Derek kept telling himself that she couldn't be dead until he, Scott and Allison headed to First National Bank and found Boyd and the other girl, who turned out to be Derek's long-lost younger sister Cora Hale. Derek found Erica's body shortly afterwards and carried it back in his arms to show it to Scott and Allison, heart-broken.
He wouldn't learn it was Kali who killed Erica until Currents, when Kali and the twins Ethan and Aiden Steiner forced Derek to kill Boyd with his claws, causing him to absorb Boyd's powers and see through his memories how Erica fought Kali to escape the bank vault but had lost her life in the process. Both Boyd and Erica's deaths shattered Derek so much that he distanced himself from his friends for some days and were some of the reasons that led him to give up his Alpha powers to heal his sister Cora from her mistletoe poisoning.
Throughout Teen WolfEdit
In Ice Pick, Derek surreptitiously broke into Beacon Hills Memorial Hospital, where Erica was taken after suffering yet-another one of her seizures at the high school. After the head nurse Melissa McCall left Erica's room, Derek entered the room and wheeled Erica's gurney to the morgue in the hospital, where he listed the side-effects of her anti-seizure medications and remarked how bad they were. Horrified, Erica questioned Derek over who he was, but Derek only hinted at the fact that both of them had a common friend, Scott McCall, and asked her about the sign she received right before to her seizures. Erica described it as an "aura" or a metallic taste in her mouth that tasted like blood. Derek caressed her head and legs as he pulled her closer to him and used his charm to offer her the means to not only be finally free of her epilepsy and the side-effects of the medications but also to have a better life. Erica asked him how he could do it and Derek flashed his Alpha eyes at her, preparing to give her the Bite.
The next day, everyone was awestruck when Erica made her entrance into the cafeteria as a gorgeous young woman wearing high heels, a miniskirt and a leather jacket, having also adopted a smug and confident posture. Scott and his best friend Stiles Stilinski followed Erica outside the school and saw her getting into Derek's Camaro as the two Werewolves smiled dangerously at the former two.
Later on, Scott and Stiles realized that their other classmate Vernon Boyd would be Derek's final choice for a third Beta in his pack and scrambled to find him before he accepted the proposal to become a Werewolf. Stiles went to Boyd's house but nobody seemed to be there until Erica showed up and knocked Stiles out with a part of his Jeep. Meanwhile, Scott finally found Boyd working at the school's ice rink, where he immediately questioned him if Derek informed him of everything that he would meet if he agreed to become a member of his pack. Boyd imparted that Derek made him aware of the Hunters that infiltrated Beacon Hills and divulged that he would still take the transformation to end his reputation as the loner who sat at lunch alone every day. Scott told him that there were much better ways of gaining friends, with Derek's not being the best example.
The two were surprised when Derek, Erica and Isaac Lahey revealed themselves and Derek urged Scott to listen to Isaac and Erica's personal views about their newly-gained powers. Erica admitted that her life became transformative after meeting Derek while Isaac commented that he felt greater than ever, despite having become a fugitive of the law, which supported Derek's belief that any human would desire their kind of power. Derek sent Erica and Isaac after Scott but he easily overpowered them because he had much more experience in fighting and attempted to tell them that Derek only cared about them as long as they gave him more power before he slided them across the rink to land at Derek's feet. Derek confirmed Scott's allegations about power and joined the fight, beating the young Beta to a bloodied pulp and leaving him wounded on the rink. Boyd approached the beaten Scott to reveal that he already got the Bite from Derek but was more interested in being a Werewolf like Scott rather than one like Derek, Isaac and Erica.
In Abomination, Derek held up a training session in his new lair at Railway Depot to help Erica and Isaac improve their fighting skills, mainly due to their poor performance against Scott earlier at the ice rink, while Boyd was on the sidelines observing the training. Isaac kept using the same tactics time over time while Erica attempted to catch her Alpha by surprise by jumping from a platform to him but Derek constantly shoved them to the ground. Disappointed, Derek suggested they try something less predictable, prompting Erica to throw herself at him and kiss him for several seconds until Derek shook her off him and demanded her to never do that again. Erica assumed it was because she was a Beta but Derek corrected her, saying he had someone else in mind for her, the then-Omega Scott, who was still in a relationship with Allison Argent.
Isaac asked Derek if they could take a break because he had bones that needed hours to heal. Derek initially seemed to sympathize with him but, at the last moment, he broke Isaac's arm and looked at him in the eyes to asseverate that the Hunters would not allow them to rest when they were at war against them. He also brought up the arrival of the mysterious shapeshifter that killed Isaac's father, an Argent Hunter and, finally, a mechanic the previous night. Until they figured out what kind of creature they were dealing with, he had to teach the three new wolves everything he knew as fast as possible.
Erica was watching the semi-final lacrosse game with Boyd up until one of the players of the opposing team known as "The Abomination" injured one of their players. When Coach Finstock required one more player so they wouldn't have to forfeit, Erica attempted to forbid Boyd from showing off his Werewolf skills like Derek told them but Boyd joined the team anyway and used his enormous size, body build and Werewolf physical attributes to help the Cyclones win the game.
Erica left the stands and caught Stiles in the principal's office searching for the Argents' Bestiary so it could help him and the others learn more about the new shapeshifter. She dragged him to the school's indoor swimming pools for Derek to question Stiles about the shapeshifter that had paralyzed him and the mechanic working on his Jeep several days earlier. Initially, Stiles played dumb and sarcastically recounted seeing lots of EPA violations that he would like to report to the authorities. Not amused by Stiles' jokes, Derek used his claws to puncture a basketball to make the teen collaborate with him, a method that left Stiles uncomfortable but it made him talk about what he really saw. Stiles described it as a slick creature with black scales, rows of teeth, slit reptilian eyes and a big tail. They were horrified to see that it was right above them and it came down to attack, knocking Erica unconscious and paralyzing Derek with its venom with no choice but to throw Derek and himself into the swimming pool while Stiles kept Derek afloat due to the latter's paralysis. They figured out that the water kept the creature at bay for unknown reasons when it got scared by touching the water.
Two hours later, Scott finally arrived from his dinner with the Argents and scared away the lizard creature. Derek and Erica met with Scott and Stiles outside the school and revealed that the lizard was a Kanima, a mutated version of a Werewolf. He only came to that conclusion when the Kanima showed fear of its own reflection and heard rumors and myths about it. Although Kanimas and Werewolves were both shapeshifters, Kanimas were more like "Abominations" like Stiles mentioned. Derek was appalled by Scott's recommendation to seek help from the Argents but Scott argued it was the more clever strategy to face the monster that seemed to be stronger and faster than either of them, not to mention their lack of knowledge regarding their newest enemy. Derek refused to work with Hunters that were responsible in the decimation of his family and swore to kill the Kanima when he found out who it was.
In Venomous, Derek, intent to know who was the Kanima, sent Erica to track down Jackson Whittemore, whom Derek had begrudgingly bitten at the end of Season 1's Code Breaker right after becoming an Alpha and showed signs of rejecting the Bite when he bled a strange black substance several episodes ago. She found him in the high school's locker room working out with his best friend Danny Mahealani and demonstrating more supernatural powers such as a heigthened sense of hearing as he was under the impression that his transformation into a Werewolf was happening slower for unknown reasons after he showed signs of rejecting the Bite back in Omega. Danny left to take a shower while Jackson was desperate to prove that he could lift much more weight than he was supposed but the weight could have fallen on top of him hadn't Erica showed up. He initially thought it was Danny who helped him but he opened his eyes to see that Erica was there and she wasted no time in grabbing Jackson by the throat.
She brought him back to Railway Depot and the first question Derek asked Jackson was what happened at the night of his first full moon back in Shape Shifted. Jackson, having been frustrated lately because he did not transform into a Werewolf as expected, bitterly replied that nothing happened, but Derek could listen to his heartbeat and determine he was lying to them. Jackson insisted that he could prove he was being honest and asked them to allow him to go home and pick up the video he made of himself sleeping through the whole night of the full moon, even though he knew the video was missing two hours of footage. Derek and Isaac sneered at Jackson for videotapping himself, angering the co-captain of the lacrosse team to the point that he ranted at his neighbour Isaac that he was preparing for the "gift" Derek promised him while Isaac was "curled into the corner suffering an existential crisis about turning into a "monster"", but Jackson apparently ended up getting nothing and reiterated that he could get the video at his house.
Derek denied Jackson's request and insisted he had a better way in his mind. While Erica and Isaac restrained Jackson, Derek put up some gloves and revealed a shard of glass left from the battle between Scott and the Kanima. Derek pointed out that they all knew a snake couldn't be poisoned by its own venom and managed to allow a single drop of Kanima Venom fall from the shard of glass into Jackson's mouth but he became paralyzed like the other victims, forcing Derek to conclude Jackson wasn't the Kanima and move on to his next suspect: Lydia Martin, who had been bitten by his uncle Peter Hale when he was still the Alpha.
The next day, Isaac forced Jackson to remove his testimony of seeing Isaac fight with his father at the night of the latter's death, allowing him to return to school. Jackson overheard Erica and Isaac planning to test Lydia with Kanima Venom during their chemistry class as per Derek's orders. The class involved the students working in pairs to create sugar crystals and switching partners over the experience. Erica profited from the fact that she was partnered with Scott to seduce him as part of Derek's plan to get Scott to join his pack and she caressed his thigh to make Allison jealous but Scott was resistant to Erica's attempts to turn him against Allison. She was then partnered with Allison, taunting her that the relationship between her and Scott wouldn't last for long and even challenging her to a "hot girl fight" in the lab. When paired with Isaac, Lydia unknowingly licked a sugar crystal that Erica and Isaac secretly covered with Kanima Venom and proved to be unaffected by it, convincing Derek and the others that she was the Kanima.
Despite Scott's best arguments to dissuade him and his pack from killing Lydia, Derek insisted that Lydia was too much of a threat to all of them and had to be put down so she wouldn't murder more innocent people or even one of them. Fortunately, Scott had a Plan B and asked Stiles and Allison to take Jackson and Lydia to the McCall House, in the guise of a study group, while he had to remain at school for a little longer. The Hale Pack members tracked them there and Erica and Isaac were ordered to break into the house to incapacitate the others and kill Lydia while Derek remained outside with Boyd. Scott arrived in the nick of time to overpower and knock Isaac out while Erica easily caught an arrow that Allison fired at her, only to realize she was tricked into catching an arrow covered with Kanima Venom; thus paralyzing her. Isaac and Erica were thrown outside, forcing the somewhat-embarassed Derek to admit that he considered Scott as the Alpha of his own pack rather than an Omega, though he reminded them that they couldn't beat him personally, but Scott countered that he had enough stengths to hold Derek until the cops arrived.
All of them witnessed the Kanima climbing up the roof of the McCall House and it hissed at them menacingly before fleeing into the town. Seconds later, Lydia came out and demanded to know what the hell was going on, proving Derek was wrong and Jackson was indeed the Kanima.
In Restraint, Derek was astonished to learn that the Kanima was still living after he thought he killed it by slashing its throat and he had not figured out yet who it was (as he was not aware that Jackson was in the McCall House with the others) so he sent Erica to get on the good side of either Scott or Stiles or both to figure out who it was. He opened up a trunk full of chains and others restraints that were meant to lock the neophyte Werewolves during the next full moon. Isaac warned Derek that the next full moon was coming and he would be alone to face the Hunters while Isaac, Erica and Boyd would be all locked up. He confessed his belief that dealing with the Argents was the bigger issue at hand and suggested they just forget the Kanima but Derek irritably yelled they couldn't as he believed that Gerard Argent had some plans with the Kanima, given the way they looked at each other the previous episode.
Scott and Stiles carried Erica back to Railway Depot after Jackson paralyzed her with his Kanima Venom and caused her to have a seizure for the first time since her transformation. Concerned for her life, Derek broke her arm to push the venom out of her system and re-trigger her healing ability, saving her. Scott confirmed to Derek that Jackson was the Kanima and accepted joining his pack at least until they save him, but they would do things his own way.
In Raving, Scott, Stiles and Derek visited Alan Deaton at the animal clinic for his guidance to come up with a plan to capture Jackson and finally find out who his master was. Deaton entrusted Stiles with creating a Mountain Ash circle around the rave, where Jackson, his master and their next target would be located. The Mountain Ash was used by many cultures to defend themselves against the supernatural and this substance would not allow neither the Kanima nor the Master to escape as long as the circle remained unbroken.
Inside the rave, Isaac and Erica were given the task to distract Jackson and sedate him with Ketamine to keep him from killing Kara Simmons, his next target. Although Jackson's master realized what they were up to and commanded Jackson to claw the two Betas to keep them from foiling his plans for Kara, Isaac and Erica quickly recovered from this attack and managed to sedate Jackson before bringing him to an empty room, where they were soon joined by Stiles. The Kanima Master used his connection with Jackson to speak to the three through the mouth of his servant and revealed that all the people he made Jackson kill in the last few weeks were the people who "murdered" him, confusing Stiles, Isaac and Erica. They began freaking out for real when Jackson seemed to be overcoming the effects of the Ketamine faster than expected and since Isaac used the entire vial on him, they had no choice but to leave the room and keep the door shut. However, Jackson, in full-Kanima mode, easily busted out out of the room and succeded in killing Kara.
Meanwhile, Derek and Boyd confronted Chris Argent and his fellow Hunters outside and managed to take them all down, except for Chris. They were hit with Wolfsbane-laced bullets, leading Derek to instruct Boyd to take his car and head to the clinic for treatment while he searched for Scott. Derek forced Stiles to break the circle to save Scott from dying. He ultimately found him in a warehouse being slowly poisoned by Victoria Argent with wolfsbane vapor and was forced to fight with Victoria, inadvertently biting her during the struggle.
In Party Guessed, Derek was opening up the trunk full of chains and other restraints to lock his Betas up during that night's full moon, which would be Isaac's second and Boyd and Erica's first. Derek asked them if they knew what the symbol on the trunk was and Boyd identified it as a triskelion or triskele. He went on to tell that the spirals were associated to many trio concepts: mother-father-child; past-present-future. He correctly infered that for Derek and his family the spirals represented the three ranks of Werewolves: Alpha-Beta-Omega. Derek emphasized that Werewolves could always rise to one rank or fall to another, with Betas becoming Alphas and Alphas falling to Betas or Omegas. Isaac interrogated him about Scott being an Omega but Derek assured him that Scott joined them and that he was monitoring Jackson at the moment before informing them that the full moon wouldn't be easy for any of them since they would be overcome with the urge of tearing anything in sight apart. Erica smirked and replied that it was a good thing that she had her period last week but quickly became disturbed when Derek pulled out a spiked headband that she would be forced to wear.
The full moon was rising and Derek and his Betas were inside the car, with Derek about to place the headband in Erica. Isaac, concerned about Erica and pointing at the appearance of the headband, asked why Erica had to wear it and Derek explained that, as a woman, she would be able to endure more pain than Boyd and Isaac before offering his first true Beta one headband as well, an offer that Isaac hastily refused. Isaac restrained Erica while Derek screwed the torturing device in her head, causing her a great deal of pain that earned sympathy from both Isaac and Boyd. Derek chained Boyd and Isaac afterwards but once the full moon hit its peak, the three young wolves transformed into their Werewolf forms and managed to break free before violently attacking Derek. Isaac briefly escaped the car by jumping through the window but soon returned in full control over himself and helped Derek subdue Boyd and Erica.
Although Isaac seemed in control over himself, Derek chained him back up just in case and was surprised to learn that Isaac was using his father as his anchor. Isaac admitted that his father used to be caring and loving until the deaths of his brother Camden and his mother affected him so much that he became the abusive man he was shown to be before his own death. Derek left his Betas in the car and Lydia, possessed by Peter's spirit, showed up and rendered Derek unconscious with wolfsbane powder to drag him to the Hale House as part of a ritual to bring his uncle Peter back from the dead.
In Battlefield, Boyd and Erica were walking through the dark woods, as Erica reminded Boyd that Derek wanted them to be back by dawn. They stopped when a howl was heard, meaning it could be from a Werewolf but it did not sound like Derek's. Many more howls were heard from all directions, unsettling the two of them and they rushed to the Hale House. They finally arrived at the House, where Derek was reading through books as he deduced that they planned to leave Beacon Hills and they confirmed that they planned to leave during that night's lacrosse game when everyone else would be too distracted. They admitted to their Alpha that it was not like they really wanted such thing, with Erica confessing that she would like to acquire her license after turning 16 the previous month but she would be unable to get it if dead. Derek reminded them that he warned them of the dangers they were currently facing before they accepted the Bite, but Boyd fired back that Derek did not tell them it would be such a dangerous situation. Derek conceded that he had not informed them very well of the downsides of being a Werewolf but taught them that being members of a pack was the only way to survive, earning surprising news from his Betas that they might have found another pack.
They recounted the howls that they heard earlier and believed that they heard like a dozen of wolves. Derek repudiated this and assumed that they heard an example of the Beau Geste Effect: the way how two wolves can modulate its howls to sound like twenty. Erica and Boyd replied that they did not care about it and insisted that they had their minds up. Derek retorted that they would be running rather than leaving and once they started, they wouldn't stop running for their lives. The two disregarded their Alpha's warnings and left the House together.
At night, Boyd and Erica realized that the howling was nothing else but a recording used by the Argents to lure them into a trap. They ran through the woods as fast as they could while being chased by Argent and Allison, the latter of whom was consumed with rage and bloodlust toward Derek and his pack, blaming them for her mother's death because of Gerard's manipulations. They eventually caught up to them and Allison fired an arrow at Erica but Boyd caught the arrow before it could hit Erica in the face. Allison fired more five or six arrows that striked Boyd in the chest and abdomen, with Erica pleading Allison to stop before she killed her close friend. Allison ignored Erica and continued to shoot arrows at Boyd, only for Argent to shoot her bow out of her hands, saving Boyd from certain death.
In Master Plan, Gerard captured Stiles at the end of the championship lacrosse game to use him to reach Scott and get him to deliver Derek to him and had his cohorts throw the young man into the basement of the Argent House. He realized that he was not alone in the dark basement when mumbling was heard and turned on the lights, finding Erica and Boyd gagged up with their hands suspending from the ceiling and bound to electrical cables that were weakening them and keeping them from escaping. Stiles shocked himself upon trying to free them and Gerard came down the basement to inform Stiles that he had been torturing the young Betas for a while but their instinct to protect their Alpha was too strong for them to give away Derek's whereabouts. Stiles confidently indicated that Scott would find him by his scent and that he could find him, even in the bottom of a sewer "covered in fecal matter and urine". Gerard was not impressed with Stiles' ability to "paint a vivid picture" and proceeded to beat up Stiles as a warning to Scott while Boyd and Erica were forced to watch this incapable to help.
Hours later, Argent came down the basement and explained to Boyd and Erica that his family had been hunting and studying Werewolves for centuries. They learned that the lowest levels of electricity could keep a Werewolf from transforming and suppress their healing factors, while higher voltages disabled their superhuman strength and the highest could kill them if necessary. Realizing that his father Gerard was the real threat after seeing how he molded his daughter to become a ruthless Hunter like him, Argent freed Boyd and Erica and allowed them to escape.
In the woods, Erica and Boyd stopped running for a few moments to catch their breaths until they heard howls from true Werewolves. They found themselves surrounded by an unknown Werewolf pack, whose members whipped out their claws, leaving their fate uncertain.
In Tattoo, Derek helped Scott make his tattoo of two bands permanent by burning his arm with a torch to repay him for his help in rescuing Isaac from an Alpha at the hospital. When Scott was about to leave, he noticed that the door was painted and used his claws to uncover the symbol of a Trinacria that was painted by the Alpha Pack at the end of the previous episode. Derek was forced to confess to Scott and Stiles that a pack of Alphas infiltrated their hometown and had kidnapped Boyd and Erica, whom he, Isaac and Peter had been searching for the last four months.
In Chaos Rising, Derek and Isaac called Peter and summoned him to Derek's loft for him to perform the memory manipulation ritual typically performed by Alpha Werewolves in order to retrieve Isaac's memories of where he found Erica and Boyd since the Alphas had stolen his memories of the location when they captured him and the ritual was a risky one that Derek never performed before. Peter stuck his claws into the back of Isaac's neck and saw glimpses and figures, one of them was Boyd inside the vault and another one was Deucalion catching Isaac spying on him in the lair. Peter confirmed to Derek that Isaac had indeed found Boyd and Erica and heard a conversation between Deucalion and the other Alpha Pack members that they planned to kill the two Betas on the next full moon, which would be the next day's night.
With the memory manipulation ritual out of their options, Scott, Stiles, Derek and Isaac consulted Alan Deaton, who suggested a procedure to get Isaac's memories back but it was really dangerous as it involved submerging Isaac in cold water so his heart-rate would be slow to the point of "nearly dead" for them to have access to his subconscious. Isaac agreed to this plan and was put into a trance, allowing him to be back in the location where he found Boyd and Erica in his memories while he gave the details of what he was seeing to the others. He eventually found Deucalion and the other Alphas and their presence made him increasingly agitated, which made Derek to impatiently demand more precise answers to what he was seeing. Isaac got out of the trance and informed them that Erica and Boyd were locked in the vault of an abandoned bank named First National Bank. When he asked why the others looked alarmed, Stiles stated that one of the last things that he disclosed was that the Alphas locked him in a room with Erica's dead body inside.
Derek stubbornly insisted that Erica wasn't dead, but Stiles countered that the way Isaac made it sound did not leave them without much room for interpretation, igniting a debate over who was the other person locked with Boyd. Scott suggested it could be the mercenary Braeden that rescued Isaac in the previous episode but Isaac was sure that Braeden wasn't a Werewolf like them but the person with Boyd was. Stiles wondered aloud if the Alpha Pack was pitting Erica and Boyd against each other during the full moons to see which one survived, which he called "Werewolf Thunderdome". This only made Derek more determined than ever to break into the bank and rescue them from the Alphas.
The next night, Scott, Stiles, Derek and Peter gathered in the loft to formulate a plan to break into the vault using the information Stiles collected from the Internet. Derek volunteered to punch through the vault's thick walls but Stiles scoffed at this idea until Derek proved it by punching Stiles' hand. Peter was against this plan of breaking Boyd and the other Werewolf out of the bank because he believed it to be a too risky move against the Alphas, particularly the twins Ethan and Aiden that possessed the power to merge into one giant Alpha, and was willing to leave Boyd and the other girl for dead, claiming that Erica was already dead but Derek was still in denial about that. Derek ignored his uncle's warnings and persisted with the plan, asking Scott to accompany him. Scott believed that they had to do their best to rescue their friends but if Erica was really dead, who was the other girl in the vault with Boyd?
Meanwhile, Deucalion, Kali and Ennis were patrolling one of the hallways of the bank, unaware that Allison was hidden in a closet under their Emissary Marin Morrell's orders to avoid being detected by the Alphas. Kali briefly stopped in her tracks when she seemed to have caught Allison's scent but the young Huntress cleverly spilled a gallon of ammonia to mask her scent. Kali shrugged off her suspicions and walked away to join her fellow Alphas. Using her phone's light, Allison looked around and discovered, to her horror, Erica's decomposing corpse sit in a chair against a shelf.
Before they infiltrated the bank, Derek noticed the anxious look on Scott's face and asked him to tell him why he was so nervous. Scott divulged that he was more concerned with the Alphas' reasons to keep Boyd alive until that time because it passed four months since they had painted their symbol in the Hale House's door and they were not certain of what they could have been planning during the summer. Derek refused to bail on the plan and leave Boyd and Erica for dead, making his willingness to risk his life for theirs clear.
Derek and Scott managed to punch their way through the vault, where they encountered an increasingly agitated Boyd growling at them. Scott received a call from Peter and Stiles alerting him to that the walls of the vault were made out of a mineral called Hecatolite, whose properties of scattering and absorbing the moonlight kept Boyd and the other Werewolf from shifting for the last three full moons, leaving them more aggresive and bloodthirsty and more vulnerable to that night's full moon. The other Werewolf revealed herself and a stunned Derek recognized her as his younger sister Cora Hale, who ordered Derek and Scott to get out of there while she and Boyd could still resist the moon's influence on them.
Morrell opened the vault's door and kneeled down to complete a Mountain Ash circle around the vault's interior, Derek and Scott with Boyd and Cora, who were unable to contain their urges any longer and succumbed to the full moon, viciously attacking Derek and Scott. Back in the closet, Allison heard the fighting going on and exited the closet to go and try to help her friends. Boyd and Cora were shown to have the upperhand during most of the fight due to the fact that they weren't holding themselves back like Scott and Derek until Boyd stabbed Scott in the stomach with his claws and lifted him up. Fearing for Scott's life, Allison broke the Mountain Ash seal against Derek's wishes, allowing Boyd and Cora to flee into the woods. Derek was furious at Allison, even though she saved his life, for releasing two killing machines to the human population but Allison refused to take the blame as Derek was the one turning teenagers into supernatural predators in his plan to build his own pack.
In Fireflies, Scott reluctantly revealed to Allison that her mother Victoria attempted to kill him back in Raving and Derek was forced to fight and bite her to save his life. Allison demanded to know why he didn't tell her the truth earlier and Scott hesitated for a few moments until he admitted he couldn't tell her as he didn't want Allison's last memory of her mother be the action of a killer. They turned around to see that Derek returned from the storage closet with Erica's lifeless body in his arms and was staring at it with grief. The three of them left the bank to try to catch the feral Boyd and Cora before they accidentally hurt someone under the full moon's influence after spending the entire summer locked in the Hecatolite-lined vault.
In Currents, Kali, furious at Derek over his supposed role in the death of her lover Ennis, confronted him at his loft, which was turned into an electrical trap for the Alphas but was sabotaged due to Kali and the twins Ethan and Aiden cutting off the power prior to their arrival. The twins showed Derek's girlfriend Jennifer Blake in their grasp and compelled Derek to fight Kali without any assistance from Boyd and Isaac by threatening to tear Jennifer apart if he refused to agree to their demands. Kali and Derek fought at almost equal terms until Stiles, Lydia and Cora finally turned the power back on, shocking and weakening Kali, Derek and a careless Boyd, but Kali was the first one to recover and enlisted the twins to hold Derek's clawed hands while she lifted Boyd. She shoved the young Beta's body against his Alpha's claws, making Derek accidentally take Boyd's powers and ultimately kill him.
Kali and the twins warned Derek that they would give him until the next full moon to kill the rest of his pack and join Alpha Pack or they would return to kill them all. Derek apologized to Boyd for putting his life in danger but Boyd guaranteed him that it wasn't his fault and his months as a Werewolf made his life worth it. Dying, he confessed to Derek that he wondered what effects a lunar eclipse would have in Werewolves like them, and Derek began seeing one of Boyd's memories back when he and Erica were still in the Alpha Pack's custody. In this memory, Erica was asking Boyd what the lunar eclipse would do to them and remarked that they lasted hours before wondering aloud if it would make them stronger. Kali was walking straight to the door to exit from the vault after watching the two for sometime and Erica set her sights on her, fiercely stating that she hoped the lunar eclipse would make them stronger. She stood up to her feet as her eyes glowed gold and she snarled and charged at Kali with all of her power. However, Erica was swiftly outmatched and whispered Boyd's name as she attempted to reach him before she succumbed to the wounds she sustained in her clash with Kali and died.
Back in the present, Boyd's body collapsed on the water and he died as well, shattering Derek. Stiles, Lydia and Cora finally arrived and Cora broke down and started sobbing over Boyd's body while Stiles attempted to comfort the guilt-ridden Derek. All of them mourned Boyd's death.
- Erica seemed to have romantic feelings for Derek when she kissed him during their training in Abomination, but Derek did not return the feelings because he wanted her to seduce Scott to break his relationship with Allison Argent.
- Derek was devastated with her death and it is unknown what he did to her body after finding it at the bank's closet.