Grimm Season 1 Episode 12

A homicide investigation leads Nick and Hank to a boxing gym and they discover that the joint’s really the supply source for a ritualistic band of brawlers. But since rule No. 2 of this particular fight club (a.k.a The Lowen Games) is “Leave the human out of it,” they enlist the help of Monroe, who in no time at all is trapped with a creepy cage neighbor.