S1, E21: After Juliette (Bitsie Tulloch) stumbles upon a brutal murder, Nick (David Giuntoli) learns the suspected creature (guest star Kenneth Mitchell), and friend of Monroe (Silas Weir Mitchell), is suffering from a mysterious condition -- the inability to completely return to human form. This mysterious condition leads them to a therapist (guest star Roger Bart) who’s created an artificial drug to suppress the creature side, with horrifying side effects. Meanwhile, the investigation takes a surprising turn when Hank (Russell Hornsby) sees something he can't quite explain. Sasha Roiz and Reggie Lee also star.