"Like the wolf, the kanima is a social creature, but where the wolf seeks a pack, the kanima seeks a friend." Allison: Waiting to kill her? Derek: But it is! Jackson: What is that? Jackson: Why's that? Lydia's immune, and somehow she passed it on to Jackson. Scott: I want to talk to Derek. Stiles: Aah.
Plan: A: the Kanima; Q: What is Jackson? A: the creature's toxin; Q: What did Lydia show immunity to? A: Derek; Q: Who wants to kill Lydia? A: Derek's pack; Q: Who did Scott, Allison, Stiles and Jackson fight? Summary: Convinced that Lydia is the Kanima, since she displayed immunity to the creature's toxin, Derek wants to kill her. Scott, Allison, Stiles and Jackson try to protect her together. After a fight with Derek's pack, it is revealed to everyone that Jackson is the Kanima.