Portland homicide detective Nick Burkhardt discovers that he is the latest in a lineage of "Grimms," monster hunters with the gift to see past their human facade. As he comes to grips with his new abilities, he must track down a killer who has abducted a young girl and plans to fatten her up before eating her.
-- Sweet Dreams, Marilyn Manson -- Sweet Dreams
Nick and Hank investigate the claim of a teenage girl who broke into a home with her boyfriend, that someone attacked her boyfriend. They soon discover that the home owners are not all that they seem. Meanwhile, Nick asks Eddy to watch over Marie when Renard withdraws the police detail at the hospital.
Nick and Hank investigate the death of a lawyer by anaphylactic shock in the middle of a flash-mob, and discover that the murderer used bee venom. As they pursue the case, Nick realizes that a monster is responsible, and is forced to defend Adalind Schade, the hexenbiest who tried to kill him.
Nick and Hank investigate the death of a woman and connect her to a B&B owner who breeds with women and uses pheromones to make his conquests. Meanwhile, a Reaper arrives in town to avenge his fallen comrade, and Renard intervenes with the newcomer.
When a teacher is apparently gnawed to death by rats, Nick learns that a violin prodigy may be responsible... and a creature as well. Meanwhile, Juliette is puzzled by a repairman's reaction to Nick, and Hank has dinner with someone that he saved.
Eddie is caught in the middle when an old flame arrives in town to investigate the death of her brother. Meanwhile, Nick is on the trial of the killer, and realizes that he has a good reason for his bloody rampage.
When a drug dealer is killed while threatening hikers, Nick soon determines that the killer is a feral blutbad and turns to Eddie for help tracking her down.
An escapee returns to Portland seeking revenge against those who put him behind bars. His unusual strength and high tolerance for pain makes Nick take notice. As the case escalates Nick and Juliette are put in danger, and Monroe is called into action to help put an end to the convict's deadly rampage.
Nick and Hank investigate a murder victim left in a dumpster, and soon discover that the trail leads to an abusive boyfriend, an arrogant lawyer, and a meek junk yard owner. Meanwhile, Juliette notices someone watching her and Nick, and Eddie gets a message from the creature community.
When a street kid turns up dead in the river, Nick and Hank discover that someone is running an organ-legging operation. However, things become even worse when Nick confirms that monsters are behind it, and prefer exotic human organs.
Nick and Hank go after a woman who liquifies the organs of her young, attractive male victims. Meanwhile, Nick discovers that word of his existence as a Grimm has spread through the creature community.
Nick stumbles upon an underground fight arena involving creatures when one of the enraged prisoners gets loose and kills two local people. Eddie agrees to go undercover to find out the arena's address, but gets abducted and is put into the ring.
A mysterious figure from Marie's past shows up when three thieves try to steal rare gold coins. Nick discovers that they bear a curse that causes anyone who touches them to fall under their influence.
When two men are immolated, Nick investigates and discovers that the killer is related to an exotic fire-dancer creature who is attracted to Nick.
Nick gets involved in a drug theft when he investigates the murder of a fuchsbau shop owner. Meanwhile, Eddie bonds with the victim's sister, and Hank falls under the sway of Adalind and Wu gets a fatal dose of the substance she's using to establish her control.
Songs: Massive Attack -- Angel, Destrophy -- Reconnect
Nick tries to take Juliette on a romantic weekend so he can propose, but they both get involved with an abusive creature husband and his wife who are living nearby. Meanwhile, Renard tells Adalind to pull Hank in now that he's hooked on her.
-- Season of the Witch
Nick and Juliette learn who Hank's new girlfriend is, while Renard orders Adalind to initiate his plan to use Hank as a means of blackmailing Nick into giving up the key that Marie left him.
A revolutionary fuchsbau from Europe comes to the U.S. and a hundjager follows him, intent on killing him. The fuchsbau goes to see Rosalee, his old lover, when he's wounded and Rosalee calls in Nick for help.
As Nick perfects his skills, he reaches out to the eisbiber community when one of their members sees a troll kill another of their kind. While they refuse to testify, the troll summons two of the Reapers to kill the Grimm. Meanwhile, Juliette invites Eddie over for dinner to thank him for saving her life.
A financier and his wife's godfather lose everything in a bad investment, and must turn to the wife's stepmother for a loan. She turns them down and turns up dead... her body shattered by ultrasonic waves. While Nick and Hank investigate the case, Juliette looks into the circumstances surrounding the deaths of Nick's parents.
When Juliette finds two corpses in the woods that appear to have been killed by Bigfoot, Nick gets involved and discovers that the murders lead to a wesen counselor who is helping other creatures deal with the inner range. Meanwhile, Hank and Juliette both come closer to Nick's secret life as a Grimm.
The mysterious Akira Kimura, who apparently murdered Nick's parents, comes to Portland looking for the cursed gold coins. While Nick goes after him, Adalind plots revenge against Juliette, forcing him to tell her the truth about his life as a Grimm.