The episode centers on the murder of Isaac Lahey's father, which leads to Isaac being taken into police custody.
Scott, Stiles, and Derek soon realize that Isaac's father wasn't killed by a normal animal or even a typical werewolf. This introduces the mystery of the "Kanima," though it isn't fully named in this specific episode.
You can currently stream Teen Wolf on Hulu or find it through various digital retailers. Teen Wolf recap – Season 2, Episode 2: Shape Shifted