Highly respected judge Logan Patterson is murdered, and shortly after several other people who played some part in the conviction and incarceration of an escaped giant of unnatural strength. Nick is badly wounded, out of action. Monroe however shows unusual enthusiasm to help out while Hank follows the paper trail.
A man named Leonard "Lenny" Drake is found dead in a garbage truck and Nick and Hank investigate the case. They find blood in the dumpster near his building and a trail of blood to the parking garage. The manager explains that the tenant was a violent man that lived in his apartment with the gorgeous Natalie Havershaw. On the previous night, they had an argument and the tenants Marty Burgess first and the lawyer Mason Snyder then had come to protect her. Marty returned to his apartment while Lenny and Mason continued to argue. Then Mason escorted her to her car and ...
When Nick consults him about an erratic murder committed by athletic ex-con Dimitri Skontos, Monroe soon helps him realize that's actually a victim of 'gladiator games' organized by the most bloodthirsty pride of Löwen, a lionesque feral species. Nick spends his anniversary working out the fighters are recruited through a dodgy parole officer and where the arena is hidden. Captain Sean Renard realizes the lucrative fights are becoming too notorious, his royal order to close down the games is ignored, so he turns to a priestly enforcer. Meanwhile first Monroe, then ...
Jeweler Sam Bertram was murdered by three European killers, of rival feral species, to steal the rarest Ancient gold coins from his safe. Two are dead, the third steals a uniform from a cop he murders. The coins are found on the elusive Farley Kolt, who is arrested and tells Nick enough to work out he was late aunt Marie's true love. The coins, minted on Zakynthos, with swastika's and lions heads, are poisonous and magically attract great power and utter disaster. Captain Sean Renard keeps them and starts an ambitious 'campaign against crime' amidst dreams of absolute...
When heavily burned bodies appears, Nick to led to a both the existence of dragons in the world of wesen and a charismatic fire-dancer for try's to spark a flame between her and nick, hiding a deadly true agenda.
Nick is in the trailer trying to find out what the key that he received from his aunt might open. Juliette calls him telling that Hank has invited them to have dinner together with Adalind. Captain Renard is forced by a criminal with a weapon to go with him to meet his cousin, but he reacts and kills them both. When Nick meets Adalind, he recalls that she wanted to kill his aunt and he confronts her near the restrooms. But he is called to investigate the murder of the two men and leaves the restaurant. Meanwhile Renard goes to the house of Catherine and she tells him ...
Nick investigates the failed attempt to murder feral Ian Harmon, who seeks help from ex-lover Rosalee, who brings in Monroe, who turns to Nick. He finds the feral hit-man Edgar Waltz is a Hundjäger ('canine hunter'), a ruthless breed used by the seven competing royal families, who demands police captain Renard's help. Waltz stops at nothing, threatening with city-wide slaughter and kidnapping Rosalee to get his prey, but Nick, Ian and Monroe still fight back, for once overruling human law.
After a man and his wife are scammed out their fortune by a Madoff-like fraudster, the husband approaches his wife's evil stepmother for financial assistance. But she refuses and is soon after murdered by a Murcielago - a bat-like creature that kills with a sonic scream.
Episodes of vicious attacks by Bigfoot-like Wesen known as Wildermann are suddenly rampant. Nick and Monroe discover that the errant Wesen are connected to a psychologist performing medical experiments to help the Wesen control their urges.
A Schakal Wesen wreaks havoc while searching for the ancient Zakynthos gold coins, while a mysterious woman in black tracks his movements. Nick informs a dubious Juliette of his heritage just before she collapses and is hospitalized because of a poisonous scratch from Adalind's cat.
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.
Monroe explains to Nick about the feral Coyotl prison gang-like, even tattooed kind's pack code when they find on old friend of Hank is actually one who fled his pack years ago and now finds his daughter kidnapped. The trail leads to their Texas relatives, the Kempfers, who stop at nothing but ignore the other side has a Grimm. Nick shows angelic patience when Juliette's memory returns about everything except their love.
Park ranger Ryan Gilko is the first of several Wesen, affected by a contagious disease, who suddenly commit violent attacks on people. The team felt relaxed now Hank is being included in the secret, so Monroe takes Rosalee on a picnic. Alas, the plague spreads and even affects her, so it's up to Monroe to make the remedy they researched together while Nick holds her feral state in check. Captain Renard meanwhile learns that another terrifying European fugitive has arrived in Portland.
Reverend Calvin, a feral wolf, reports a fortune stolen from church funds and the parishioner who did the accounts, a feral sheep like most of his flock, missing. The man is later found cut-up in the grinder of his employer's factory, but has no motive or suspicious record. Undercover as a 'homeless' seeking church shelter, Monroe discovers reverend Calvin, whose previous Southern parish was similarly robbed presumably by a parishioner, has an affair with his sheep church secretary, who transferred with him, but is up for a rude surprise too.
Nick is delighted when Juliette, who still can't remember him, invites over for a home cooked dinner to get acquainted all over. But he's called away urgently by Monroe, who has a feral visitor: a ruthless killer, yet also a friend of his, who only pretended to take a contract for Monroe's death to warn him after 'accidentally' killing the initial hit man. Nick, who wants her for at least two earlier murders, grudgingly cooperates, going so far as to allow her to pretend to be his partner. To get to the royal presumed to have hired the killer, Monroe must fake his ...
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.
Nick is puzzled by several cases where a suspect who escaped the police is violently dealt with by a masked, cloaked avenger. He even leaves Nick messages, suggesting he is a 'real Grimm' who is cleaning up 'weakling' Nick's messes. But he strikes terror even with gentle Wesen, like the beavers, who seek help through Monroe, who fears it's a descendant of a medieval Grimm vigilante order. Nick suspects a police mole.
Nick is shocked about Juliette's infidelity, which she can't explain, yet sort of accepts it and ends up moving out to his heritage trailer. Monroe realizes from a TV appearance that Juliette's partner, who ordered an obsession cure, is none other than Police Captain Sean Renard and ends up telling Nick. Meanwhile Adalind and a pack of canine Wesen almost hunt down Renard for the key, and he locates Nick's trailer after allowing him to lock up Adalind.