Erin comes to Suffolk County Hospital to receive antibiotics for a scratch she received from a mangy dog during the last full moon. When Josh hears her story, he realizes that she has been attacked by a werewolf. After discussing the situation with Nora, and scaring off Erin's social services worker, who reveals Erin has had many problems, they reveal to Erin that she is a werewolf by showing her old footage of Josh from the storage unit. The night of the full moon, she and Nora go out to the woods for her first change. Nora believes it will happen to herself first, but Erin suddenly transforms and nearly attacks Josh in his car on the hill. Josh, brandishing a revolver, attempts to defend himself until Nora has completely changed and subdues Erin herself, first through physical strength, and then through their wolf bond.
Erin stays with the group for a while, convincing Sally to try to get a new identity, until she runs away when Josh catches her with Nora's brother R.J, who is several years her senior. Josh and Nora try their best to find her, but Liam eventually delivers her back to their doorstep. However, it is all a plan Liam has put forward to get Erin to help him kill Aidan. He gives her a cellphone to communicate back to him, as she searches though the house for Aidan's blood supply. She taints it with her own blood, but the situation escalates when Aidan comes home just as she finishes her job. He drinks the blood, and realizes too late that it had werewolf blood in it. As he lies on the floor, bleeding from his orifices, she calls Liam who rushes to the house, all the while keeping her eyes on Aidan while holding a wooden stake. In defense, Aidan kicks her, slamming her into a wall, causing massive head trauma. She fades in and out of consciousness over the next few days, until Liam goes to her bedside, and proclaims she has done her part for the pack and smothers her with a pillow, killing her.