After their face-off with Kimura, Nick finds himself trying to come to grips with the return of his mother, Kelly Burkhardt. A trail of brutal murders unveils a foreign conspiracy to hunt down Nick, leading to several revelations about his past. Meanwhile, Juliette still lies in her mysteriously-induced coma as Rosalee and Monroe work tirelessly to bring her out of it safely. Elsewhere, Hank struggles with the shocking truths he's recently seen and Captain Renard deals with unexpected family issues when his estranged brother comes back into his life.

As Nick and his mother continue to battle the Mauvais Dentes, Monroe and Rosalee fight against the clock to save Juliette. More details are revealed about the source of Juliette's illness, resulting in an epic showdown. Back at the precinct, Hank senses that something is amiss when Nick lands in hot water with the FBI. Meanwhile, Captain Renard continues to reveal himself as he deals with his estranged brother.

Even Nick is puzzled by the case of two murdered teenage favorite candidates to the high-school general knowledge quiz qualifying for the state competition. Wesen in the story belong to several species, one extremely rare. Captain Sean Renard wins a community prize and turns to Monroe for a medicinal cure for his sexual obsession with Juliette Silverton. Surviving competitor Pierce Higgins is actually an unwitting Wesen cross breed. In Vienna, Renard's brother, Prince Eric, confides unto his latest conquest.

After sleeping on it Nick decides it would be best for Monroe to take Juliette to the trailer. However, the trailer triggers more memories of Nick than Juliette may be able to handle leading her to seek the help of Pilar for insights into her current condition. Meanwhile Monroe fears Rosalee, who is serving jury duty, maybe under the influence of a toad dropping Ziegevolk who is jury tampering to win his case. Nick, Hank, Bud, Monroe and Rosalee hatch a plan to stop this Ziefevolk once and for all.

A mysterious drug related force begins to turn residents of Portland into feral zombies, meanwhile, Juliette learns more of the wesen community in the spice shop.

Nick is back on lovers' terms with Juliette, who remains eager to learn about ferals. Nick must however give priority to the violent crime wave caused by zombies. As he feared, they are created by the voodoo 'baron', who sets a trap as instructed. Captain Sean Renard informs Nick about his mistrusting meeting with visiting European royal half-brother Eric and the counterfeit documents Eric had prepared at the castle. Still in Vienna, Adalind, poisoned by Pech to switch appearances, is seen roughly overtaken by the gypsy witch's family Popescu. Rosalee prepares a zombie antidote, but once tracked down in the port, the superior zombie numbers corner down Nick's party.

Nick's destiny is uncertain as zombies continue to overrun Portland.

Monroe (Silas Weir Mitchell), Hank (Russell Hornsby), Rosalee (Bree Turner) and Juliette (Bitsie Tulloch) track down a manic Nick (David Giuntoli) and do all they can to find him and reverse what's been done to him before he causes any more damage. Meanwhile, Captain Renard (Sasha Roiz) does his best to clean up the zombie fallout on all fronts - domestic and international. Elsewhere, the more time Adalind (Claire Coffee) spends with Stefania (guest star Shohreh Aghdashloo), the more disturbing things seem to get in her quest to regain her Hexenbiest abilities.