Nick joins forces with his mother to chase the sadistic `mauvais dent' monster murderers, who are after six golden coins, part of the key to a terrible secret that has been kept since the Crusades. 

Nick and his mother battle the Mauvais Dentes; details about the source of Juliette's illness are revealed; Hank thinks something is amiss. 

Hank tries to help an old friend whose daughter has gone missing, and in the process gets closer to understanding what he has seen. Nick is forced to intervene and make a decision on whether or not to tell Hank or not. 

During the investigation of an accident site, Nick discovers a disease that is quickly spreading; Monroe and Rosalee come across an infected wesen; Capt. Renard gets a tip about a dangerous fugitive. 

A feral wolf who is a Reverend reports that a fortune has been stolen from the church funds, and that the treasurer is missing. When the treasurer turns up dead, Monroe goes undercover to learn more about the Reverend's flock. 

Angelina (Jaime Ray Newman) comes to town with bad news; Nick asks Hank for help keeping Monroe safe; Capt. Renard has a visit from a former acquaintance (Alice Evans). 

An investigation into a grisly murder leads Hank and Nick to a seemingly unstable man who is on the run with his daughter; Monroe realizes that filling in for Rosalee will be harder than he thought. 

A high school student is killed by a lion-like wesen following an academic quiz. Nick and Hank join the investigation just in time to discover more murders of people connected to the quiz. 

Nick realizes a series of child abductions that he is investigating bear a striking resemblance to the Hispanic legend of "La Llorona." 

When a vicious vigilante murder makes the news, it sends Portland's Wesen community into a panic. When Nick investigates further, he discovers a pattern of violence that matches that of a particularly brutal line of past Grimms. 

Craig Wendell Ferren's execution is announced. This leads Hank to tell Nick that, with his new knowledge of ferals, he now believes Craig's protests that the murders he was convicted for were committed by mythical creatures. 

Nick is shocked about Juliette's infidelity and moves out to his heritage trailer. Meanwhile Adalind and a pack of canine Wesen almost hunt down Renard for the key. 

Nick deals with the consequences of learning the truth about Juliette and Capt. Renard; Nick must investigate his own crime; Wu responds to a shooting at Nick's house. 

Three young adult Wesen are committing robberies using their Wesen appearances as masks. Nick's police team are on the case, as well as the Wesen Council, who see it as this is a blatant violation of the centuries old Schwaben code. 

In quick succession, people are attacked by a fly Wesen, which causes blindness by licking its victims. When Nick is afflicted, Monroe and Rosalee realise they only have a few hours to create a cure. 

In Dominick Spinner's successful Portland games design company, several employees engaged in developing and testing a single video-game are murdered, one by one. 

Hank goes on holiday, leaving Nick and Renard to team and investigate a new case. A local geologist who took volcanic rock samples from Mount Hood dies by being cooked from the inside out. 

A farm worker is killed when he accidentally bumps interrupts a blue-fluorescent feral performing a raid on cattle. The case is complicated by an alien-hunter who is on the pursuit of the ferals. 

A muselike wesen possesses the ability to influence people she approaches; Juliette tries to clear the air with Nick; Rosalee visits Aunt Marie's trailer. 

Hank and Nick encounter zombies while Adalind is caught in a feud between Stefania and Frau Pech. Also, Juliette asks Monroe to reveal Nick's darkest secret.