After Juliette stumbles upon a brutal murder, Nick learns the suspected creature, and friend of Monroe, is suffering from a mysterious condition — the inability to completely return to human form. This mysterious condition leads them to a therapist whos created an artificial drug to suppress the creature side, with horrifying side effects. Meanwhile, the investigation takes a surprising turn when Hank sees something he can't quite explain.
Recap / Grimm S 1 E 21 Big Feet
He stripped off his skin and tossed it into the fire and he was in human form again.