Back at the spice shop, Monroe finds himself involved in a situation he never saw coming. Nick and Hank discover a new kind of strange when they investigate suspects being found dead - for the second time. In his jacket Jacob finds a letter from their mother urging them to go to her brother in Spain. Even after the wedding has taken place, jealous Jacob tries to get his sister away from Diego. Is there another Grimm in town, or is Nick dealing with a sadistic copycat? Nick and Hank join forces with Valentina Espinosa, a mysterious detective from Albuquerque, to help find and capture the elusive suspect.
Meanwhile, Nick and Juliette continue to figure out the rules of their relationship as a dangerous opponent lurks in the shadows with his sights on Nick. Meanwhile, a surprise visit at the spice shop gives Monroe more than he ever bargained for. Nick discovers a muse-like Wesen with the ability to influence those she gets close to — some with positive results, others with terrifying ones. To Jacob's astonishment, Marie wants to marry Diego. Nick must find a way to get close without losing himself in the process. When this doesn't succeed, Jacob starts to provoke his brother-in-law.
After Nick learns about Juliette and Captain Renard, he must deal with the consequences. When a local Reverend reports that his church has been robbed, Nick quickly learns that it's a Wesen church, and enlists Monroe to check for any suspicious activity regarding the shepherd's flock. A trail of brutal murders unveils a foreign conspiracy to hunt down Nick, leading to several revelations about his past. A romantic day out for Monroe and Rosalee takes a dangerous turn when they encounter an infected creature that is out for blood. Nick finds himself fighting a wildly different sort of nature freak in a desperate attempt to keep a volcano from burying Portland in lava. Once in Spain, it turns out that their uncle is dead. Meanwhile, Juliette seeks out help after becoming overwhelmed by the latest side effect of her recovery — multiple memories of Nick showing up everywhere.
Angelina comes back in to town with bad tidings as Monroe learns his continued cooperation with the Grimm may come at a high cost. Meanwhile a pregnant Adalind meets a powerful new ally in Europe. Things get even more complicated when Nick is called to investigate his own crime. While investigating an accident site, Nick comes upon a bizarre and gruesome Wesen disease that is spreading quickly. Juliette arranges a dinner date with Nick in the hopes of clearing the air, but their plans go awry as the case intensifies. After investigating a grisly murder, clues lead Nick and Hank to a seemingly unstable father who is on the run with his daughter. Meanwhile, Captain Renard takes it upon himself to offer Juliette comfort in handling her ongoing dilemma with Nick.
After their face-off with Kimura, Nick finds himself trying to come to grips with the return of his mother, Kelly Burkhardt. Diego lives with his sick, domineering sister, Teresa. Meanwhile, a return to the trailer brings a flurry of memories of Nick rushing back to Juliette. . Marie meets Diego, a wealthy charming Spanish surgeon, and falls in love with him. In other police matters, Captain Renard deals with an unwanted infatuation while we learn an old accomplice of his has been spending time with his family in Europe.
Meanwhile, Juliette still lies in her mysteriously-induced coma as Rosalee and Monroe work tirelessly to bring her out of it safely. Meanwhile, Captain Renard continues to reveal himself as he deals with his estranged brother. Nick and Hank are called to the scene of a murdered high school academic decathlete and learn just how competitive some extracurricular activities can be, and the extremes some coaches and parents will go to give students the best chance for success. As Nick investigates further, he discovers a pattern similar to that of a particularly brutal line of past Grimms. In Europe, Adalind finds herself in the middle of a feud between Frau Pech and Stefania while working over the details of her pending transaction. Back at the precinct, Captain Renard brings Nick and Hank in on his own recent dealings with the Verrat, to keep them on their toes.
She has her eyes set on Nick and those closest to him — especially Hank and Juliette. Meanwhile, Monroe celebrates the holiday in fine style as he teaches the neighborhood bullies a lesson. Mysterious cow mutilations and reports of glowing creatures put Nick on a case that forces him to question the existence of aliens within the Wesen world. Meanwhile, Captain Renard finds himself paying unwarranted attention to more than one woman from his past. It soon transpires that no-one will go unpunished for this. Meanwhile, Stefania and Frau Pech methodically use their alliances with Adalind to battle one another.
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