After the events at Monroe and Rosalee's wedding, Nick is faced with losing his identity as a Grimm. Hank and Juliette join Nick as they try to figure out how to deal with Trubel as she faces the consequences of a heinous murder she committed. Meanwhile, when Wu arrives at the scene, his discoveries bring back images of his traumatic encounter. A new threat arrives in Portland to steal the memories of its victims, leaving them in a state of dementia. Elsewhere, Captain Renard's life hangs in the balance and Adalind falls into Prince Viktor's trap as she desperately searches for her baby.
As Nick and Hank turn their attention to a string of attacks where victims are left without their memories, Nick weighs whether or not he should regain his Grimm abilities. Trubel joins the investigation and puts herself in harms way. In Vienna, Adalind is being held captive and learns that she is more connected than ever to Nick. Meanwhile, Captain Renard continues to fight for his life as a mysterious visitor arrives to help him.
After Nick ) has a bizarre, unsettling vision, he and Hank find themselves on a case that takes them into the world of boxing. Trubel finds herself under the watchful eye of Agent Chavez before jumping into the ring to help with Nick's investigation. Meanwhile, Monroe and Rosalee get some unexpected help in figuring out a way to restore Nick's Grimm abilities. Elsewhere, Adalind encounters a mysterious visitor in her dungeon cell.