Zombies descend on Portland.
A new case may threaten Nick and Juliette's progress in getting back to how things used to be.
Nick faces another worldly mystery that makes him question what he knows about the Wesen world.
Things heat up in Portland when Nick faces a villain unlike any other.
While on jury duty, Rosalee (Bree Turner) tasks Nick (David Giuntoli), Hank (Russell Hornsby) and Monroe (Silas Weir Mitchell) to help stop a defense attorney from using his particular "Wesen wiles" to overturn what should be an open-and-shut murder case. Back at the precinct, Captain Renard (Sasha Roiz) brings Nick and Hank in on his own recent dealings with the Verrat, to keep them on their toes. Meanwhile, a return to the trailer brings a flurry of memories of Nick rushing back to Juliette (Bitsie Tulloch).
When a gruesome homicide brings an office party to a screeching halt, Nick (David Giuntoli) and Hank (Russell Hornsby) find themselves battling a Wesen on a completely new platform - online. Meanwhile, Juliette's (Bitsie Tulloch) mysterious hallucinations finally start to take shape, giving them a whole new meaning.
When a mysterious case of sudden blindness causes a woma's death, Nick (David Giuntoli) and Hank (Russell Hornsby) come across a disturbing Wesen that feeds off its victim's tears. Meanwhile, Adalind (Claire Coffee) contemplates the significance of her new situation, while Juliette (Bitsie Tulloch) continues to work with Rosalee (Bree Turner) in an effort to fix her memory.
The Wesen code of honor comes into question when Nick (David Giuntoli), Hank (Russell Hornsby) and Monroe (Silas Weir Mitchell) discover a series of bank robberies with Wesen using true natures as their disguises. Meanwhile, Juliette (Bitsie Tulloch) finds herself tormented by faint, slowly returning memories that cause her to question her mental state.
After Nick (David Giuntoli) learns about Juliette (Bitsie Tulloch) and Captain Renard (Sasha Roiz), he must deal with the consequences. Things get even more complicated when Nick is called to investigate his own crime. Meanwhile, the search for the key intensifies as Captain Renard finds Nick's trailer and makes a surprising alliance. With Rosalee's (Bree Turner) help, Monroe (Silas Weir Mitchell) informs Nick that they might be able to stop what's going on with Renard and Juliette before it goes too far. Elsewhere, Wu (Reggie Lee) responds to a bizarre shooting at Nick and Juliette's house.
Adalind returns to wreak havoc in everyone's lives and avenge her mother's brutal death. She has her eyes set on Nick and those closest to him - especially Hank and Juliette. Elsewhere, Captain Renard's obsession continues to escalate. Meanwhile, a surprise visit at the spice shop gives Monroe more than he ever bargained for.
Hank starts reflecting on an arrest he made earlier in his career regarding a man who committed murder claiming "self-defense against monsters." With the man's death sentence rapidly approaching and the knowledge he's recently gathered from Nick, Hank begins to wonder if there was more truth to the man's seemingly absurd story then he once thought. Back at the spice shop, Monroe finds himself involved in a situation he never saw coming.
When a brutal vigilante homicide is made public, it sends Portland’s Wesen community into a frenzy. As Nick (David Giuntoli) investigates further, he discovers a pattern similar to that of a particularly brutal line of past Grimms. Is there another Grimm in town, or is Nick dealing with a sadistic copycat? Meanwhile, Captain Renard (Sasha Roiz) takes it upon himself to offer Juliette (Bitsie Tulloch) comfort in handling her ongoing dilemma with Nick. Russell Hornsby, Silas Weir Mitchell and Reggie Lee.
Despite the enthusiastic anticipation of the city's residents for Halloween, a series of horrifying child abductions make their way to Portland, quickly spoiling the holiday spirit. Nick and Hank join forces with Valentina Espinosa, a mysterious detective from Albuquerque, to help find and capture the elusive suspect. Juliette joins their investigation, acting as the precinct's fill-in Spanish translator. The more Nick digs into the case, the more he realizes the pattern of the kidnapping matches those in the famed Hispanic horror story "La Llorona," a story with its roots intertwined with his own family's history. Meanwhile, Monroe celebrates the holiday in fine style as he teaches the neighborhood bullies a lesson.
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. 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. Elsewhere, Monroe continues to manage the spice shop and gets a visit from an unlikely customer.
After investigating a grisly murder, clues lead Nick and Hank to a seemingly unstable father who is on the run with his daughter. As they learn more about the case they realize that the girl's father may be the least of their worries. At the spice shop, Monroe finds out filling in for Rosalee isn't as simple as he'd hoped it would be. Meanwhile, Captain Renard finds himself paying unwarranted attention to more than one woman from his past.
Angelina comes back in to town with bad tidings as Monroe learns his continued cooperation with the Grimm may come at a high cost. Nick comes to Hank for help to keep Monroe safe and Hank uses this time to get caught up with his knowledge of the "Wesen world." Meanwhile, an old European acquaintance pays Captain Renard a visit, but it's hard to tell if this visit is for business or pleasure.