The team has their hands full with Liam and Malia when the full moon arrives. The 'Axe Murderer' harms Peter and reveals that Derek is next on his 'list'. Lydia cracks the code and finds a list of all supernatural creatures in the town.
As another name is scratched off the list, Lydia is required to find the second key, thus revealing more targets. Scott, Stiles and Kira are on high alert after realizing that the assassin is on the lacrosse team.