He stripped off his skin and tossed it into the fire and he was in human form again.

There aspiring cryptozoologists, Michael Patterson, Dave Gimlin, and Vera Saldona, are in the woods hunting down Bigfoot at night, and filming everything they do on camera. Dave does his Bigfoot call and then they hear something moving. Following the sound, they find a fresh kill and something lunges out of the woods at them. As Vera runs off, the intruder kills Michael and Dave.

Rancher Thom Carson hears something disturbing his horses and goes to investigate. He sees a large animal attacking one of them and opens fire, driving the creature off. When he discovers that one of horses’ necks is badly scratched, he call vet Juliette to examine it. When she gets there, she confirms that whatever attacked the horse had an unusually large bite radius. Thom takes her to the spot where the animal broke through fence and discovered large human footprints with spots of blood in them. There are also tufts of some unusual hair caught in the fence. After taking a sample, they follow the tracks and find the corpses of Dave and Michael.

Nick is at the trailer examining the map locket that Marie gave him when Juliette calls to tell him what she’s found. Nick and Hank take a CTU team to the crime scene and secure the area. The bodies appear to have been attacked by an animal, even though the only footprints are of bare feet. Wu finds the hunters’ camera but before they can check it out, a bloody Vera stumbles out of the words, crying and claiming that Bigfoot attacked her two friends.

Back at the station, Nick and Hank tell Renard what they’ve discovered. According to the footage on the camera, the killer was wearing a red flannel shirt, meaning it’s murder rather than an animal attack. Vera is in the hospital and the detectives plan to talk to her when she’s in stable condition.

Later at home, Juliette talks to Nick about the murder. He assures her that it was a human being but she points out that if the same thing attacked the hunters and the horses then it can’t possibly be human.

Monroe smells something in his house and wakes up. When he goes down to investigate, a huge figure looms out of the shadow and attacks him. The intruder is wounded and Monroe easily subdues him, and discovers that he’s a friend, a wildermann named Larry McKenzie. As he gets Larry onto the couch, Monroe realizes that someone shot his friend in the leg. Larry is in his wildermann form and unable to transform, and then passes out from the pain but doesn’t revert to human form.

A reporter calls Nick in the middle of the night and asks for a statement on the “Bigfoot Murders.” When he goes to the station, he discovers that reporters have gathered and that a doctor at the hospital leaked the story. While Renard gives a press statement, Monroe calls Nick and tells him that he’s seen the news reports and that the supposed killer is on his couch. Wu informs the detectives that they found a wallet that may belong to the killer, and Nick leaves for Monroe’s house while Hank joins the police dog squad that is trying to pick up the killer’s scent.

Juliette calls a lab tech she knows and asks him to run a DNA test on the hairs that she found at Thom’s ranch.

When Nick gets to Monroe’s house, the blutbad explains that what Nick is seeing is what everybody would see because Larry hasn’t transformed back. Monroe sure that his friend is no killer and explains that Larry was meeting with a wildermann therapist, Konstantin Brinkerhof. Brinkerhof has a reputation for helping wesen deal with their savage inner beasts.

Monroe hears the police dogs approaching and they realize that they’re following Larry’s scent. Since Monroe has marked his territory, the dogs won’t come onto his lawn. Monroe puts on Larry’s shirt and leads the dogs off, ignoring Nick’s advice. Hank runs ahead of the police squad and follows the dogs. Monroe, in his blutbad form, frightens the dogs off and then turns and runs out of the woods. He knocks over Hank without harming him and runs away, but Hank gets a good look at his face.

Back at the house, Monroe tells Nick what happened with Hank. Larry staggers over to them, ripping at the back of his neck, and pulls out a small device before collapsing, dead. Upon his death, he finally transforms into his human self. Nick says that they’ll have to move the body just as Hank calls to tell his partner what he saw. Hank figures that he saw the killer because he was wearing the same red flannel shirt as the killer on the video. Nick and Monroe take Larry’s corpse into the woods and plant it near where Hank encountered Monroe, and put the neck device nearby. Monroe says a few words over his friend and then tells Nick that something must have driven Larry berserk and he plans to find out what.

Brinkerhof is at a book signing talking about embracing one’s inner self. Afterward, Nick comes over and asks to talk to him privately about Larry. Once they’re alone, Nick insists on answers using his status as a Grimm, and Brinkerhoff admits that Larry suffered from impulse control but was making progress under his treatment. Hank calls to tell Nick that they found Larry’s body and he matches the description on the wallet they found earlier. As Nick leaves, Brinkerhoff admits that he finds the idea of a cop/Grimm intriguing and suggests that they talk about it sometime. Nick assures him that he doesn’t need therapy but Brinkerhof warns him that eventually the inner man always comes out.

Juliette examines the hair samples on her own but is unable to identify them as anything other than primate.

Nick meets Hank in the woods where Larry’s body was found. Hank insists that Larry now looks nothing like the person who attacked him earlier. A CTU tech informs the detectives that the neck device is a drug delivery implant. Nick tells him to check the serial number and discover what country manufactured it, while Renard gives another press statement to the press saying that the case is closed.

That night, two homeless men, Wallace and Harold, are caped near a water tower. Wallace goes out into the woods to relieve himself and Harold hears something attack his friend. He grabs a board to defend himself and accidentally impales the creature that leaps out to attack him.

The police are called in and Harold tells Nick and Hank what happened. Hank points out that the killer is in the same condition as Larry, with bare feet and torn clothing. Wu checks the dead killer’s ID and confirms that he’s Alan Evercroft, a lawyer with a family of three. Nick examines Evercroft’s body and confirms that he has a drug implant device just like the one that Larry had.

Juliette’s friends call back to inform her that the DNA test is inconclusive, and that the hair samples appear to have come from a being with both human and animal DNA. Once she gets the test results, Juliette starts doing research on genetic chimeras: half-human/half-animal beings.

Monroe goes to a bar owned by Reynaldo, a wesen who hosted the support group for Larry and the others. He tells Monroe that the last time he saw Larry was three months ago when the wildermann came in and said that he had a foolproof cure. Larry convinced two other members, Evercroft and Dan Murray, to go with him to Brinkerhof, who had the cure. Reynaldo hasn’t seen any of them since.

The CTU tech informs Nick and Hank that the drug in the implant pump was a mixture of legal steroids and herbs. While they trace the serial numbers on the units, Monroe calls to tell Nick about Brinkerhof’s involvement with Larry and the other two wesen. He’s shocked to learn that Evercroft is dead, and Nick tells his friend that the dead man had the same pump in his neck. Monroe says that he’ll call Murray, while Nick warns him that they don’t have anything connecting Brinkerhof to the deaths.

When Monroe calls Murray, he gets his brother Travis, who tells him that Murray died two days ago. He tore up his apartment in a berserk fury and then fell out the window to his death.

Nick passes on Murray’s name to Hank, who confirms that he died of an apparent suicide and had the drug pump in his neck as well. Wu gets the report on the serial numbers and tells the officers that the company sold Brinkerhof four of the units. They have three of the pumps and Renard tells them to find out who has the fourth.

Brinkerhof is working at his office and starts to lose control of his wildermann nature. Monroe arrives and demands an explanation. The psychiatrist explains that they came to him because they were willing to give up control so that they could be free of their inner selves. However, Brinkerhof admits that he rushed his experiment and didn’t fully test the drugs he was administering. He loses control again and takes out the bottle, but drops it when he convulses. Before Monroe can help him, Brinkerhof transforms into his wildermann form and attacks Monroe. Monroe fights back in his blutbad form and Brinkerhof leaps out the window when Nick and Hank try to break in. By the time the detectives get inside, Monroe reverts back to human form and the officers chase after Brinkerhof.

Brinkerhof goes on a rampage, attacking pedestrians and then breaking into a theater reception. The wildermann knocks out one woman and drags her up into the theater catwalks. Nick and the others climb up in pursuit and the Grimm finds the woman, left behind and unharmed. When Brinkerhof sneaks up on him, Hank shoots the wildermann and saves his partner. The wildermann dies in the fall and Hank runs up to him just as he transforms back into human form. Nick claims that it was a trick of the light but Hank is clearly unconvinced and starts to panic.

Later, Monroe and Reynaldo share a toast to their three departed friends. On the news, the press reports the official story that Brinkerhoff wore a Bigfoot mask to disguise himself.

At home, Juliette tells Nick what she found out about the hair samples. Nick tries to suggest that the lab results were a mistake, but Juliette wonders if there might be real monsters out there like the one that attacked the horses and the cryptozoologists.