In Durham, Washington, a woman enter a biker bar, picks up a man named Barker, and takes him outside. Once they're alone, she rips open his throat with her claws and then tears open his chest.
Sam and Dean decide to take some time off and drive to a beach to drink beer. Dean claims that he's good but Sam isn't entirely convinced. The brothers end up discussing a newspaper article about three savage deaths in Durham, and Sam suggests that they refer it to some other hunters. Dean suggests that they check it out themselves, figuring that it'll be an easy case. Sam isn't so sure, but Dean says that he needs to get out and do some work after what he's gone through. His younger brother agrees, but only if Dean warns him if anything is going sideways.
The Winchesters go to the King County sheriff's office posing as game rangers and the sheriff explains that the three victims' hearts were consumed. He refers them to a biker named Tommy who saw the killer. The Winchesters talk to Tommy at the bar and that the woman who killed Barker is a ghost. Tommy explains that he saw the woman at an abandoned farm two nights after Barker was killed. He turned around and drove back, but the girl had disappeared in a matter of seconds.
Sam and Dean drive to the farm and split up to enter the house. There are dead chickens in the yard and claw marks on the door. Inside, Dean hears a girl talking to someone on the phone, but she smells Dean and tries to run. Sam manages to grab her and realizes that it's Kate, the college student who became a werewolf and that the Winchesters let go. They tie her up and Kate claims that despite her vow to avoid killing, she "evolved" when the hunger became too much for her. Dean is ready to kill her on the spot, but Sam talks to him privately and suggests that he kill Kate, figuring that Dean isn't ready. As they talk Kate extends a claw and starts cutting through her ropes.
As the brothers talk, the sheriff calls Sam and says that the killer has struck again... less than an hour ago. They realize that Kate couldn't have gotten back to the farm by the time they found her, just as Kate cuts herself free and runs out. Dean figures that Kate is protecting the real killer and checks her cell phone. Her last call was to the Lincoln Motel and the brothers head out. Dean wonders why Sam thinks he's not ready, and suggests that Sam might not be ready. He reminds his younger brother that Sam was the one who convinced Lester to sell his soul, which led to his death. Sam defends himself, saying that he did some dark things to get Dean back, and Dean suggests that they both need some time off.
The next morning, Sam talks to the motel clerk and confirms that Kate checked in by herself. A blonde woman wearing a hoodie comes out and the brothers follow her to a nearby park. She approaches a jogger but then walks past him, and Sam and Dean order at gunpoint to turn around. It's another girl that looks like Kate, and she says that her name is Tasha. Tasha claimed that she rented the motel room and that she knew the jogger and was going to surprise him. When Dean draws a silver blade to test her, Tasha transforms into a werewolf and attacks the brothers. As she prepares to kill Dean, Kate arrives and yanks her back, and Tasha runs into the woods. Dean tries to shoot her but Kate steps in the way and says that Tasha is her younger sister. The Winchesters demand to know what's going on, and Kate admits that she turned Tasha. Dean points out that she killed a man a year ago, but Kate insists that she had to kill Brian because he went crazy.
The trio goes to a diner to talk privately, and Kate assures them that she'll kill herself is he loses it. She has been feeding on small game and using yoga to restrain her werewolf side. When Kate fled a year ago, she went home but couldn't approach her family without endangering them. Tasha was in a car accident and mortally injured, and Kate went to her hospital room to say goodbye. However, she decided to cure her sister by turning her. Tasha recovered and Kate tries to teach her how to control herself, but her younger sister eventually started feeding on men.
Sam realizes that Kate was trying to save her sister by pretending to be the killer, and Kate insists that Tasha needs her more than ever. She plans to take Tasha deep into the woods away from humans, refusing to abandon her even after Dean warns that it's too late. Kate points out that she killed Brian when he lost control. Considering, Dean says that they have a cure but they need Kate to take them to Tasha. Kate reluctantly agrees and offers to take them to where Tasha is hiding.
As they go outside, Sam asks what Dean is doing since there is no cure. Dean reminds him that they're hunters, and their job is to kill monsters. Sam notes that Kate is just doing the same thing they do: look out for each other. Dean wonders if Sam should bother looking after him since he still has the Mark of Cain, and it's still making him a ruthless killer. Sam tells him not take out his personal problems on the sisters, and Dean wonders what Sam plans to do.
That night, the brothers drive following Kate's directions to her family cabin. Once she dozes off, Sam admits that there he also killed monsters while trying to find Dean. He defends what he did, pointing out that Dean died in his arms and then disappeared afterward. When Dean sheepishly says that he never thanked Sam, Sam says that he never has to and Dean figures that they're back to work. They find the cabin and Kate wants to go in first to explain things to Tasha. Dean handcuffs her to the steering wheel and she realizes that they lied to her about a cure. Kate insists that it's her fault but Dean says that there's no going back for Tasha. He heads for the cabin and Sam reluctantly goes with him, ignoring Kate's pleas.
The brothers enter the cabin and Sam finds Tasha in her bedroom holding a doll. She says that Sam isn't going to shoot her. When he wonders why, a man comes up holding Dean hostage. Sam has no choice but to drop his weapon, and a second man comes in with Kate. Tasha explains that she's creating a new family and turned the two men, Brandon and Travis. When she prepares to kill Sam, Kate objects, saying that she was trying to protect her. Tasha reminds Kate that she led the Winchesters there, and tells her that she can walk away or join her new pack. Kate refuses to leave and Tasha tells her to prove her loyalty by eating Sam's heart. After a moment, Kate says that she won't and Tasha tells her pack mates to take the Winchesters into the next room and kill them. She then tells Kate that she's tougher and stronger, and she's not afraid of people walking all over her anymore. However, she tells Kate that they can still be together, killing anyone who gets in their way.
In the next room, Sam and Dean taunt their captors until one of them comes in close enough for Sam to kill him with a hidden silver blade. The other man goes after Dean and Sam manages to kill him as well.
Crying, Kate tells her sister that she loves her and they hug... and then Kate stabs her with a silver knife. When Sam and Dean come in, they find Tasha's corpse on the floor and Kate gone out the window.
Later on the road, Dean says that Kate did too good. Sam wonders if they went back to hunting too soon, and worries about the Mark. Dean doesn't want to talk about it and says that he just wanted to do something good. Kate calls them on her phone and Sam thanks her for her help. Dean advises her to keep moving because they'll kill her if they meet her again, and Kate says that she will try but can't make any promises. She then hangs up and walks away.
In the Impala, Dean admits that Sam might be right, but he has to do the right thing because he's tired of doing the wrong things.
Written by Gadfly on May 22, 2016