The zombified Nick proves to be more than the Baron can handle, and crashes the plane while still over the Portland area, where he wreaks havoc at a bar. Adalind begins the trials to regain her powers. Williamson ether synthesis is used to treat the Portland zombies.

After the attack at a local neighborhood house that Nick barges into; Rosalee manages to cure Nick. Later, the coverup over his rampage conflicts with his duty as a cop when he realizes a man died during the bar brawl and he was the cause of it.

Disturbing crime scenes resurrect an old feud; news spreads about a royal family member's demise; Rosalee and Monroe talk about their relationship.

While investigating a drowning, Nick and Hank discover a group of water-bound Wesen; Rosalee unpacks at Monroe's; Renard comes to a realization about the royal baby.

A serial killer is linked to the Latin American myth, El Cucuy. Juliette learns more about Nick's mother.

A child kills a priest during an exorcism. The Wesen Council deem it an abomination and dispatch an assassin, while Juliette has an alternative theory.

A deadly crime wave may be linked to a 100-year-old urban legend. Meanwhile, Adalind meets up with Eric's cousin, Prince Viktor (Alexis Denisof), who is seeking justice for his deceased kin, and Capt. Renard responds to the attempt on his life.

An old Wesen tale of an evil Santa Claus-like creature "Krampus", a South German word for pick, cramp (iron)^[9] may be linked to a case involving missing delinquent teens. Meanwhile, Monroe asks Juliet to help him surprise Rosalee for their first Christmas together; and Renard's tour of Europe brings him closer to Adalind.

Nick and Hank investigate a Wesen with healing abilities that may do more harm than good for those around him. Juliette allows a friend, Alicia, to stay at her house after a recent issue with Alicia's husband. Hank puts the moves on his physical therapist. Captain Renard has a warning for Adalind.

Nick and Hank investigate what seems to be a Wesen gang feud, but things get very complicated when the only witness to the murder is the brother of the therapist Hank is flirting with. Meanwhile, Nick and Juliette finally decide to tell Juliette's friend, Alicia (a Fuchsbau), that Nick is a Grimm.

Someone is murdering veterans who were accused of atrocious crimes during service, leading Nick and Hank to investigate evidence of a manticore involvement. Meanwhile, Rosalee and Monroe are visiting Rosalee's estranged mother and older sister. Meanwhile, Adalind is beginning to get her powers back.

While Monroe and Rosalee start making plans for the wedding and preparing to welcome Monroe's parents, Juliette tries to contact Nick's mother. Nick and Hank are called to investigate the deaths of several officers whose scalps were taken by the killer.

Monroe tries to convince his parents regarding his life choices and decisions. Juliette assists Nick on the wesen aspect of the cop-killing scalper case. Renard must contact Adalind to help keep her safe.

When a dangerous wesen called an Aswang sets its sights on a childhood friend of Sgt. Wu, Nick and Hank must figure out how to deal with it as the investigation escalates. Adalind starts the preparations for a special delivery.

Nick and Hank find themselves in conflict with an organization called the Beati Paoli when an ancient Egyptian sarcophagus containing mummified wesen remains has been brought to the surface. This battle later gets heated up when the Wesen Council, unexpectedly, gets involved. Meanwhile, an ally of the resistance is compromised while protecting Adalind.

When a double homicide leads Nick and Hank to a strange wesen carnival called; "Carnival Metamorphosia", Monroe and Rosalee go under cover to find out what's going on behind the scenes. Sebastian makes a sacrifice on Adalind's and Meisner's behalf.

An unexpected ally arrives to make sure that Adalind and the baby get out of Europe safely; Rose and Monroe's wedding preparations remind Juliette and Nick of their past complications.

The royals call in a corrupt FBI agent and two Verrat to find Adalind's baby and kill Adalind and Renard at the latter's place. When Prince Viktor shows up, Nick, his mother, and Sean devise a plan to end this standoff once and for all. After Adalind names her baby Diana, Sean separates Diana from Adalind and hands the baby to Viktor. That night, Nick, Sean, Hank, Monroe, and Kelly disguise as Laufer and retrieve Diana. The next day, Kelly relocates the baby to a remote secret hideout.

When dangerous Wesen are found dead, its initially thought that they were killed by another Wesen. But turns out it's another Grimm, a young girl named Theresa "Trubel" Rubel (Jacqueline Toboni^[20][21]) who doesn't know what she is, but has a Grimm's fighting skills. Nick takes her under his wing and brings her to the trailer. Meanwhile an angry Adalind begins plotting revenge against Nick and Renard for giving her child Diana to the royals.

The exsanguinated body of a teenage girl known for shoplifting is discovered. Using the wound pattern Nick identifies the culprit as a Lebensauger, a Wesen species previously encountered in "The Hour of Death" (Season 2, episode 10). Seeing this as an opportunity for Trubel to get some field experience, Nick takes her along. When the investigation reveals that the girl belonged to a shoplifting ring and was held against her will, Trubel decides to join it on her own in an effort to bring the culprits of the murder down herself. Later that day, an elderly man arrives in Portland holding the last of the seven treasure keys that the Verrat want.

During a dinner with Rosalee, Monroe, Trubel and Juliette, Nick gets a strange call from a man named Josh Porter. His father, Rolek (seen at the end of the previous episode), is dying and wishes to pass on his many valuable Grimm possessions to Nick since he fears his disbelieving son will sell them to the highest bidder. Complications occur when the rogue FBI agent from "The Law of Sacrifice" returns leading a special task force from the Verrat called "Ahnenerbe", whose assignment is to retrieve any rare valuable occult and supernatural items. In this case, it's the Porter family's treasure key. While this all occurs, Adalind begins gathering ingredients for a doppelganger potion that allows her to temporarily disguise as Juliette.

Monroe and Rosalee proceed with their marriage despite an incident with the dress, and everything seems to be going well. However, Adalind begins a new plot against Nick at Viktor's request, and it threatens to ruin the wedding as well as Nick and Juliette's relationship... and Nick's future as a Grimm. Disguised as Juliette in a romantic mood before the wedding, Adalind sexually transmits a spell that later disables Nick's Grimm abilities. Sean breaks into Catherine's storage room, finds out Adalind's plot, and obtains an antidote potion to reverse the spell on Nick. The disguised Adalind meets Trubel and leaves the house before the real Juliette returns. Trubel follows Adalind a few blocks into town, where Trubel sees Adalind board a taxi cab and the disguise expire inside. Meanwhile, Juliette returns from the hair salon and sees evidence of sexual activity in the bedroom. Trubel returns and sees the couple leave for the wedding. Sean comes over to Nick's house to deliver the potion, only to find Trubel there. She gives him the wedding address. As Sean heads out, the rogue FBI agent suddenly fires three shots at his torso. The shooter chases the lone witness up to her room, threatens to kill her, and woges. Upon his sight of her identity, the Grimm kicks the intruder out the room and beheads him with her machete.