Grimm Season 1 Episode 17 (04/13/12)
Nick and Hank investigate the murder of two foreign men who happen to be family of Renard. Who also happened to kill them and cover his tracks.
Adalind and Renard form a pact to lure Nick and his key out by furthering Adalind’s control over Hank, and the only way Nick can cure Hank is to kill Adalind with his Grimm blood. Nick is able to do so, but Adalind doesn’t physically die, she only loses her power.