Nick adjusts to the loss of his Grimm powers and tries to figure out how to deal with Trubel as the fourth season opens. Meanwhile, Wu has an unpleasant flashback; a new group of Wesen come to Portland and steal people's memories; Capt. Renard fights for his life; and Adalind's desperation to find her child lands her in Prince Viktor's clutches.

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.

Nick and Hank are called to an unusual crime scene with a victim who appears to have died from clay-induced asphyxiation. At the precinct, Wu begins to grow more suspicious of Trubel’s presence. At the Spice Shop, Elizabeth makes a major breakthrough with regards to restoring Nick’s powers, while Monroe and Rosalee experience cultural backlash as a result of their inter-Wesen marriage. In Europe, Adalind hopes that putting trust in her mysterious visitor will help her escape the dungeon.

A woman claims a very persistent, talking wolf drove her to the point of madness when she's questioned by Nick and Hank after committing a deadly crime. Meanwhile, Nick and Juliette wonder if getting his Grimm powers back is worth the sacrifice of a normal life; at the same time, Bud hopes Trubel can help with a wesen-related issue; threats against Monroe and Rosalee intensify; and Adalind's perilous trek to retrieve her daughter continues in Austria.

The justification for Nick to become a Grimm again is made much clearer in the wake of the most recent attack against Monroe and Rosalee. At work, Nick and Hank are called to a stretch of highway that acts as a staging area for a horrifying Wesen ritual. In Vienna, Viktor meets with a completely broken Adalind, now ready to be of assistance in finding and retrieving the baby. Meanwhile, Trubel is surprised by the sudden arrival of an old friend.

Nick and Hank are called to investigate a bizarre string of home invasions that lead to an even stranger Wesen phenomena. Monroe has a very special Christmas surprise in store for Rosalee. Meanwhile, Truble comes to a life changing realization that will affect everyone.

An unsuspecting traveler brings a blood-sucking legend with him to Portland, and Nick and Hank find themselves investigating the gruesome trail of "El Chupacabra." Meanwhile, Monroe and Rosalee prepare to leave for their long-overdue honeymoon as they are met with more threats regarding their marriage. Elsewhere, Viktor and Adalind decide to take a trip of their own, while Wu decides to confront Nick about what he has been seeing.

Nick and Hank must save Monroe from the Secundum Naturae Ordinem Wesen while Juliette considers life as a Hexenbiest.

After Monroe’s abduction by the Wesenrein, Nick gathers the whole team, including Wu, to track him down and return him to Rosalee. As the search intensifies, Juliette learns more about her new reality as a Hexenbiest.

Nick and Hank investigate a homicide at an abandoned -- and supposedly haunted -- residence.

Nick and Hank investigate a series of murders that lead back to the Wesen Council and a mysterious bounty hunter. Elsewhere, Juliette’s meeting with Henrietta brings about more disturbing news than she was expecting. Meanwhile, Adalind and Viktor make their way back to Portland.

When an arson case looks to have Wesen origins, Nick (David Giuntoli) find himself reluctantly having to ask an old foe for help. Elsewhere, Viktor (guest star Alexis Denisof) teaches Adalind (Claire Coffee) the effectiveness of well-played diplomacy. Meanwhile, Juliette (Bitsie Tulloch) finds herself in a confrontation sooner than expected.

A murder victim missing a foot leads Hank and Nick to a disturbing discovery.

Nick and Hank are called to investigate a one night stand turned deadly when a man finds himself in the middle of a very bizarre love triangle. Captain Renard hopes Monroe and Rosalee can help him deal with recurring episodes of phantom bleeding. Meanwhile, Adalind makes a discovery that might turn the tables in her favor and Juliette makes a big decision that could change the course of her relationship with Nick.

A cyclist's homicide introduces Nick and Hank to a Wesen with a tragic fatal touch. Captain Renard and Adalind learn the Royals have stepped up their efforts to find their child, and another member of the Royal family is introduced. Meanwhile, Juliette ponders the idea of embracing what she's become as opposed to fighting it.

Nick and Hank are called to investigate a rare Wesen that leaves its victims frozen solid. Meanwhile, Juliette starts to feel that she is losing her humanity as she seeks to get revenge on Adalind. Elsewhere, Captain Renard continues to suffer from mysterious bleeding and visions while Monroe works toward coming to grips with the Wesenrein incident.

A homicide leads Nick and Hank onto the dark and mysterious path of a local Native American power quest. Meanwhile, Juliette's erratic behavior lands her on the wrong side of the law. At the spice shop, Rosalee and Monroeare on a mission and call on Captain Renard for help.

Nick and Hank investigate a homicide they discover is linked to a wesen rite of passage.

A string of homicides have the press asking Captain Renard if a Jack the Ripper copycat has arrived in Portland. While dealing with the investigation, Nick, Hank, Monroe and Wu deal with a situation they never expected. Meanwhile, Adalind and Rosalee must work together on a last ditch attempt to fix Juliette's condition. Elsewhere, Juliette decides to help her new ally even if it means hurting those around her.

While investigating a grisly murder, Nick and Hank get closer to uncovering the identity of the serial killer while Wu's life is put in grave danger. Having turned down Monroe and Rosalee's offer, Juliette solidifies a new alliance as she works to get her revenge. Elsewhere, Trubel makes a surprising return to Portland.

On the heels of a shocking discovery, Nick is hell bent on getting revenge and taking the fight to the Royals with help from Trubel. Meanwhile, Juliette's alliance continues to lead her down a dark path.