A bizarre double homicide leads Nick (David Giuntoli) and Hank (Russell Hornsby) to a boxing gym, which Nick discovers is a supplier for a darker, ritualistic fight club in the creature world. When Monroe (Silas Weir Mitchell) lends a hand and gets in over his head, Nick must dig deep and find his inner "Grimm" to defend him. Bitsie Tulloch, Sasha Roiz and Reggie Lee also star.