The episode begins with a blue sedan throwing a woman out in front of a hospital. The woman is alive, but badly injured. At home, Castle notices that food has been disappearing from the fridge. He suspects the maid. Martha tells him that the maid hasn’t been coming for the past three days. Castle is determined to find out who has been stealing food. He tells Kate that he is going to take bold steps to put a stop to this. They arrive at the crime scene and Esposito tells them that the woman was dumped in front of the ER, but she didn't make it. Castle finds it weird and Kate thinks that the killer must have developed a guilty conscience.
Esposito tells them that the women from the ER did not see the driver. Kate tells him to set up a canvas around the hospital. They go to the coroner and he tells them that the woman’s face is disfigured with claw marks, but he cannot tell her what kind. The coroner also tells them that the victim sustained her injuries 5-6 hours before she died. Ryan tells Kate and Castle that the victim’s name is Anne Cardinal and she was doing her PhD in Evolutionary Biology. Esposito arrives and tells them that Anne worked at a retirement house called the Haven House. It is a sanctuary for primates like apes, chimps etc., who retired from the movie business.
Kate and Castle go to the sanctuary and talk to Dr. Paul Devlin, who was Anne’s faculty adviser. He tells Kate that on the day of the murder, Anne had an argument with a guy in the parking lot. She left early because she had something important to do. He also tells her that Anne did not spend a lot of physical time with the primates. Castle notices one of the primates, Moonshine, and thinks that she is slightly violent. At the precinct, Esposito tells Kate that they got a hit on the blue sedan. It is registered to Eddie Malson, who is a convicted killer. He also has a pit bull, named Bad Ass. They bring in Eddie for questioning. Eddie tells Kate that he found the victim in an alleyway and she was all messed up. He could not leave her lying there, so he dumped her in front of the ER. He knew that if he stayed, he will be a suspect because he has a record. He shows the team the spot where he found Anne. They go to the spot, and Kate believes that Eddie was telling the truth.
They notice giant footprints, and Castle concludes that Anne was killed by Bigfoot. Kate is more interested in the footprints found near the body. These prints are too big for a guy like Eddie. She feels that these prints could be a good lead. At the precinct, Ryan believes in the Bigfoot theory, but Esposito thinks that Bigfoot is a hoax and all the reported sightings are people angling for money. Ryan pulls out Anne’s call records, and the last call she made was to Dr. Darrell Meeks. He is the world’s foremost authority on Bigfoot. Esposito has managed to get the sketch of the guy Anne was arguing with. Kate and Castle go to meet Meeks, and Ryan and Esposito go to meet the coroner. The coroner tells them that the cause of death is blunt force trauma to the head. He also found some glass shards in the wound and it has an anti-reflective coating.
He says that this glass was pounded into her head. He then hands them a pendant and tells them that the victim swallowed it 5-6 hours before she died. It was around the same time when she was attacked. Castle and Kate talk to Meeks, who tells them that Anne called him because she thought that Bigfoot was present in the city. It turns out that Anne gave him a big Yeti finger. Meeks’ wife, Garland, arrives and she thinks that the Bigfoot is nothing but a hoax. Meeks tells them that a television show caused for strange people to follow Anne, out of curiosity, hoping she would lead them to Bigfoot. They know the guy Anne was having an argument with, Chase Diggins. He is a Bigfoot hunter from Australia. They show Kate one of Chase’s pictures, which shows that Chase has a prosthetic hand. The hook at the end of his arm could have caused the damage to Anne’s face. Ryan and Esposito leave to find Chase.
Kate and Castle interrogate Chase, who tells them that he was in the alley the night before Anne was murdered. He found her putting fake prints at the scene. He believes that Anne found the real thing and was trying to throw him off the trail. That is why he confronted her and they ended up having an argument. Kate believes that Chase is either crazy or he is lying. Esposito tells her that they did not find Anne’s DNA on the hook, and his alibi checked out. Esposito tells them that the glass shards were from a camera, but there was no camera at the crime scene. Ryan arrives and tells them that the pendant Anne swallowed belonged to her roommate and friend, Justine Bolton. He says that Justine was murdered a year ago and her boyfriend, Kurt Wilson, was a suspect. However, Kurt fled and hasn’t been seen since then.
At home, Castle has set a trap for the thief. It turns out that Alexis is the one who has been stealing food from the fridge. The next day, Ryan tells Kate and Castle that Anne was looking into Justine’s murder, and he believes she might have found Kurt. Esposito arrives and tells them that they tracked the serial number on the lens, and Anne had a Cloud account. They access the account and find some footage. It shows that Anne was attacked in the woods, not in the alley. Kate and Castle talk to the tech, who examines the footage, and they narrow down the area where the murder took place. It is in the middle of the woods. Kate and Castle hike to the crime scene. They end up falling in a trap, a huge hole in the ground. Castle helps Kate to get out of the hole. She goes to get some help.
At the precinct, Ryan tells Esposito that one of Anne’s neighbors saw Kurt go into Anne’s apartment. They arrest Kurt. Later, Ryan calls Kate and tells her that Kurt is not talking. Kate goes back to rescue Castle, and Bigfoot appears. She is about to shoot the creature, when it falls into the ditch. Castle freaks out. It turns out that Bigfoot is a fake. It is Meeks in a costume. He admits that he followed Anne into the woods, with the hope of finding Bigfoot. He tells them that he found a bloody club in the woods.
At the precinct, Kate shows Kurt the club. Kurt admits that he was hiding in the woods. He says that Anne brought him food and other supplies. He says that few months ago, he came out of hiding and begged Anne to look into Justine’s murder. Anne believed that he was innocent and agreed to help. Kurt tells them that he and Justine were in love and were planning to leave town. He tells them that it looked like Justine was scared of someone, but she never told him who. Anne told him that she was close to finding some answers. He believes the killer found out that Anne was onto him, so he killed Anne. Kurt tells them that the killer must have taken Justine’s pendant because, when he found her body, it was missing. He is sure that the killer is someone Justine knew very well, because she opened the door for him and let him inside her room. Kate is now certain that Anne did find Justine’s killer because the pendant was recovered from Anne’s stomach.
Kate and Castle confront Devlin. Kate made some inquiries about Devlin and found out that he taught in four different schools. There were charges of stalking, obsession, and sexual harassment. They also know that Justine had scheduled a meeting with the Dean to tell him why she was leaving Hudson. They theorize that Devlin was afraid of what Justine would say in the meeting, so he killed her.
Anne found out that Devlin killed Justine, so he followed Anne into the woods and killed her. Kate reveals that his cell phone places him at the crime scene. Devlin doesn’t say anything. Kurt thanks the team. At home, Alexis apologizes for stealing. She tells Castle that she ran out of money because she donated her entire allowance to a friend, Jonah, for his vision. Castle is relieved and they go out for dinner. The episode ends.