Those grieving for a deceased loved one becomes the target of a revolting fly-like Wesen who feeds on tears and leaves behind a deadly parasite.

A young geologist is gruesomely burned after collecting rock samples from a nearby volcano, and it finds Nick and the rest trying to stop a demonic Beast who is literally hot to the touch.

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.