A rancher shoots into the dark to scare something attacking his horses. Juliette arrives to inspect the horses and finds one with large claw and teeth marks around the neck. Investigating further, Juliette and the rancher find large footprints and traces of blood heading back into the forest. As the tracks fade away deeper into the woods, they find a shoe with a foot still inside of it. Startled, they discover the rest of the body and another corpse lying on a nearby fallen tree. Juliette wonders what could've done this and calls Nick.
The police arrive to examine the scene. Hank notes the wounds look like they were made by an animal; however Nick counters the footprints appear human. Sgt. Wu decides it's obvious: it's a man carrying a wolf! Discovering a video camera, the detectives hope it was running during the attack and can shed some light on the situation. Out of the bushes comes a distressed woman, clearly still in shock. She begins raving it was Bigfoot who killed her friends... he killed them and he's still out there!
Back at the station, the bodies are identified as two crypto-zoologists, aka Bigfoot hunters. Their surviving friend is sedated at the hospital, yet her claims of being attacked by Bigfoot have already hit the press and are creating a stir. The found video footage definitely shows something attacking them, though it seemed to be wearing a red flannel shirt. What animal wears clothes? Nick shares his findings with Juliette who disagrees. If it's the same thing that attacked the horse, it was not a man.
Monroe hears something with heavy footsteps lurking around his house. When Monroe finds this Wesen creature instead of being scared, he says, "Larry?" It's an old friend from Monroe's Wesen support group. Monroe brings Nick over to show him an injured Bigfoot unconscious on his couch. Larry is a Wildermann, a Bigfoot-type Wesen normally known as smart loners who like being in nature. Even asleep, Larry is unable to change back to his human form, which is unusual. They can't take him to a hospital or a police station looking like this without raising too many questions. Monroe smells the search dogs outside and realizes they're about to find a wanted-for-murder Bigfoot at his house. All they're missing are the torches and pitchforks.
Monroe puts on Larry's red flannel shirt so he can lead the scent somewhere else. Running through the forest with the dogs right behind him, Monroe waits until an isolated location to transform into a Blutbad and scare the dogs off with a howling shriek. As the dogs run away, Hank heads toward the sound. The Blutbad Monroe charges at Hank and knocks him to the ground. All Hank can make out is a red shirt matching the video description. That and the shape of a Wesen creature contained within. What was that?!
After Monroe returns to his house, Larry wakes up and screams at them to "get it out" as he reaches into the back of his neck and pulls out a strange device. With the device removed, Larry reverts to his human form, apologizes for his actions and crumbles to the floor dead. To protect Monroe's involvement, Nick plants Larry's body near where the dogs were frightened, leaving the odd device in Larry's hand for forensics to examine. Monroe still can't fathom any of this. Larry was showing great progress with this famous psychiatrist to control his Wesen urges. Monroe delivers a touching eulogy in German ending with the saying: Everything has an end. Only a sausage has two.
The police believe the case is closed upon discovering Larry's body in the woods, though Nick visits Dr. Brinkerhoff, Larry's psychiatrist, for more information. Brinkerhoff immediately tries to get into Nick's head instead of answering his questions. Nick deflects his Hannibal-esque intentions. Brinkerhoff shares he was working with Larry on his impulse control issues using therapy only. Drugs are an infective and only partial solution for people with Larry's condition. Recognizing Nick as a Grimm, Brinkerhoff offers his services. For men in darkness, it's not a question of if they'll be seen in the light... only a matter of when.
Another Bigfoot attack occurs and the suspect is actually killed during the assault. The attacker was a happily married lawyer with three kids and no priors. Nick and Hank agree it fits the pattern of the previous killings. Could it be a copycat? Nick checks the back of the lawyer's neck and finds the same device found on Larry. Meanwhile, Juliette is handling her own investigation using the hair sample she found at the ranch. According to the DNA results, the hair came from a single organism with the traits of two different types of species. Juliette looks up the phrase Para-Human: a term used to describe a human/animal hybrid.
Monroe meets with an old friend from the therapy group he shared with Larry, Reynaldo. Reynaldo recalls that the last time he saw Larry he was acting like he'd been cured with the conviction of a religious convert. Larry's enthusiasm led two of their other friends to visit Dr. Brinkerhoff, and Reynaldo hasn't seen any of the since. Monroe asks why Reynaldo didn't follow the crowd as well in the search for a solution? Reynaldo shrugs; quick fixes aren't his style.
The forensics team reveals the neck devices are pumps used to release a steroid in the subjects. Tracing the devices to the manufacturer, the company informs the detectives four of these pumps were shipped to Dr. Brinkerhoff. Nick connects the names Monroe supplied him from his therapy group to the Bigfoot lawyer and a suicide plunge. More than ever, Nick needs to find who has the fourth device implanted in their neck. Monroe knocks on Dr. Brinkerhoff's office door looking for some answers just as the doctor starts to transform against his will on the other side. The fourth pump is in him!
Temporarily suppressing his urges, Dr. Brinkerhoff explains he honestly believed he'd found a cure with the drug he gave Monroe's friends. However, when the dosage seems to drop, the patients would become suspended in the middle of their transformation and be unable to return to their human form. Dr. Brinkerhoff's transformation completes and he flees his office just as Nick and Hank arrive. Pursuing the doctor to the top of a theater, Hank shoots him off the balcony. On the floor level, Hank sees Dr. Brinkerhoff's body de-morph from Wildermann to human before his eyes. Twice now, he's witnessed something unexplainable. Nick denies anything happened, but Hank is persistent. "I'm telling you, it just changed!"
Monroe and Renaldo share a toast in honor of their departed friends and the battle they fought against their animal nature. While the media is reporting the scenes of Dr. Brinkerhoff running around the city as a hoax caused by someone wearing a mask, Juliette isn't so sure. She shares with Nick her findings from the hair sample. Juliette is well aware this sounds odd, yet for the first time, she's really starting to wonder if there is a Bigfoot. What if all of those stories we've heard through our lives aren't really stories? What if they're real? Nick just sits there not knowing what to say.