In the town of Fenton, Pennsylvania, a boy chases a girl across the high school football field. He catches her and they run off to the bleachers to kiss. The boy hears something but the girl ignores it. A man staggers onto the bleachers, his face rotting off, and grabs the girl. The boy shoves him back and the couple recognizes him as Mr. Howard.
Rachel brings her date Sam Girardi back to her apartment after dinner. He comments on her ability to identify the ingredients in their meal and they start to kiss. Rachel’s enhanced sense of touch goes out of control and she asks a confused Sam to leave.
The next morning, Rachel refuses to discuss he date with Nina. Rosen comes in and tells them that they now have government badges identifying them as members of the Defense Criminal Investigative Service, the DCIS. Afterward, Rachel goes to her office and takes a call from her mother. Rosen inadvertently comes in and admits that he knows what happened, but Rachel refuses to discuss it with him. The doctor asks her to come to Fenton with him about a situation that Sullivan reported.
As they arrive in Fenton, Rosen explains that there have been three strange deaths and the victims suffered rapid-onset organ failure. The CDC has found no pathogens to indicate a cause. Rosen admits that he didn’t expect to use their new IDs so soon and warns Rachel that their mandate is changing. Rachel smells the fear of the people in the town and hears them gossiping about what are causing the deaths. They meet with Dr. Vanessa Calder, the CDC expert who is just preparing to leave town. She explains that each victim suffered damage to the amygdala as if they were exposed to a sudden shock.
At the sheriff’s office, Rosen and Rachel find Sheriff Marty Handell arguing with Coach Kent Zelanski, who demands answers and worries that his players are upset. Zelanski suspects that Handell is holding out on him and storms off. Handell explains that the first victim was Ned Burton, the son of football star David Burton. Another man was a bank manager and the third was the school guidance counselor, Mr. Howard. Handell mentions a fourth death but dismisses it as a coincidence. When Rachel takes an interest, Handell explains that the first death was a car crash involving Chris Elkhart, a local teenager. There was no autopsy but Rosen wants to see the body.
Rosen and Rachel go to see Chris’ mother, Jessica, and request permission to exhume her son’s body. She explains that her husband died of cancer when Chris was 12. Since then, he has already considered Jessica his best friend. Rosen asks if anything unusual happened when Chris died and Jessica explains that he tried out for the football team and was rejected by Coach Zelanski. Zelanski made him the equipment manager and got on Chris for everything, constantly shouting at him. Chris refused to quit and let the team down. Rachel, upset at Jessica’s story, breaks into tears and tells Jessica that Chris was lucky to have a loving mother. She hugs Jessica, who agrees to let them exhume the body.
As they leave, Rosen asks Rachel if she’s okay. She says that it won’t happen again but Rosen says that it will and it’s okay. Rachel explains that her mother won’t return her calls and Rosen figures that her hearing Jessica describing the loving relationship with Chris upset her. That night, they go to see Handell at the station. She smells decay and hears one heartbeat, and they follow the odor into the holding cell area. The dying Handell attacks Rachel and Rosen manages to pull him off before the sheriff can harm her. As he dies, Handell says that they should have listened and he should have stopped it.
The next day, Rosen calls in the rest of the team. Rachel steps outside to leave a message for her mother to call back. Rosen informs them that Handell’s cortisol levels were five times higher than a normal human’s. Cortisol is a hormone produced when the body undergoes stress, eating away at muscles and organs. The waitress comes over and realizes that they’re Federal agents. She figures that a serial killer is responsible and Rosen assures her that they’ll let everyone know when they figure out the cause. Bill checks Zelanski’s file and confirms that he’s connected to four of the victims. Rosen isn’t sure how to proceed and Bill is glad to provide his expertise.
The team goes to the school and Bill and Nina talk to Zelanski while the others canvass the high school. Gary checks the emails and confirms that Zelanski was sending messages to David Burton. Nina and Bill talk to Zelanski, who starts yelling at them. Nina uses her power and pushes him into cooperating.
They report back to Rosen, informing him that Zelanski is a jerk but he isn’t a killer. Bill confirms that David Burton’s name was in Handell’s files for vandalism and bullying. Gary wanders off, following emails about David’s bullying. He finds David and his friends bullying a younger student. When Gary reads off some of the emails with insults about David, the football player and his friends come after him. Cameron knocks them down and takes out Zelanski and his assistant when they try to hit him. David runs off and Cameron trips him with a thrown book. The football player goes into convulsions and Rosen assures Cameron that he didn’t hurt the boy.
While Rosen, Nina, and Gary accompany David to the hospital, Rachel, Cameron, and Bill go to the sheriff’s office and go over what they have on David. They don’t find anything unusual but Bill confirms that Chris Elkhart had no damage to his amygdala. That suggests that the car crash was an accident, but Bill takes Cameron with him to investigate the crash site while Rachel goes back to talk to Jessica.
At the hospital, Nina discovers that Gary has taken David’s jacket. Rosen confirms that Davis is suffering from the same symptoms as the other victims. His body is producing cortisol as rapidly as they can flush it out and Rosen realizes that David is in withdrawal. There no substance in his blood to be addicted to, and Rosen concludes that he’s addicted to a person, the same as the other victims.
Calder returns to check on David, having asked the hospital to call her if there was another case. When Calder takes David’s hand, he stabilizes. Rosen has her let go and David’s condition gets worse, and he explains that when someone shows David signs of affection, his brain manufactures oxytocin, a “love hormone.” As they administer oxytocin, Rosen figures that the Alpha killer formed a strong bond with each victim and then severed it.
Rachel tells Jessica what her team has learned. The mother is unimpressed with the news that David is dying, and explains that they thought Chris was weak and treated him as an outsider. They ridiculed him and spread rumors about him on the Internet, and Chris idolized them and never understood why they targeted him. Jessica asks when Rachel will be joining the others, confirms it’ll be another 30-45 minutes, and then offers to make Rachel something to eat.
Bill and Cameron check out the crash site and Cameron analyzes it with his hyperkinesis. The road conditions on the day of the accident were good and Cameron realizes that Chris killed himself.
The oxytocin treatment saves David’s life and Calder wonders what is causing the addiction. Rosen refuses to tell her about Alpha involvement and Calder admits that she knows about government secrecy. David wakes up and says he needs to see the person responsible, but passes out before he can give a name. Bill calls to tell Rosen that Chris killed himself and Handell covered up the suicide. All of the victims were part of the cover up and ignored Jessica’s demands for an investigation, and Cameron points out that Rachel went to see Jessica.
Rachel identifies the ingredients in Jessica’s cookies and then admits that her parents think she’s a freak. She tells Jessica that she’s an Alpha with enhanced senses, and that her parents think that she’s sick and pray that they can find someone to marry her. Rachel breaks into tears as her cell phone rings with a call from Bill. She tries to take it but Jessica says that it can wait and hugs her... and Rachel’s skin glows as she feels wonderful.
Cameron and Bill arrive at the Elkhart house and come inside. Rachel and Jessica are gone and Rachel’s cell phone is abandoned on the table. She’s with Jessica, who is driving out of town. Rachel has told Jessica everything about herself and her team and complains that she doesn’t totally trust Rosen as a non-Alpha. Jessica says that they have to make one stop and then she’ll need Rachel’s help to escape.
Nina has Gary ping Jessica’s cell phone. While he works, Nina talks to Rosen, who is driving after Rachel and Jessica. He believes that Chris’ death triggered a psychotic post-partum depression in Jessica, and that Rachel is emotionally and physically vulnerable. Gary locates Jessica’s cell phone and gives directions to Cameron and Bill.
Jessica tells Rachel that she learned of her ability when Chris was born. At the funeral, David’s father Ned came to him, crying, and she comforted him. When he admitted that he knew how David drove Chris to his death but did nothing, Jessica sent him away and the man died the next day. When Rachel tries to convince her to turn herself in, Jessica momentarily releases her and withdrawal symptoms set in. Jessica tells her that if she helps her, she’ll feel better.
Gary tracks Jessica’s cell phone and directs Bill, who is arguing with Cameron over who should drive Bill’s car. Bill ends up going off the road and breaking the axle, and he floods his system and starts running after Jessica. Rachel spots him in the rear-view mirror, and Jessica realizes that he’s there and the others are close as well. She pulls over, pulls Rachel out of the car, slaps her, and tells her that she should die. As Jessica drives off, Bill finds Rachel as she starts to deteriorate.
Jessica goes to see Zelanski at his home and he embraces her. He wants to feel better and Jessica says that he and the others murdered Chris and now he’s going to die alone.
Cameron and Rosen arrive and the doctor gives Rachel an oxytocin injection. However, her ability means that the deterioration is spreading faster. Rosen has her focus on him and his voice and he tells her that real love is unconditional and what Jessica is making he feel isn’t love. He tells Rachel that she’s like a daughter to him and always will. Cameron and Bill join in and Rachel concentrates, and she recovers.
Zelanski insists that he would do anything to bring Chris back, but Jessica tells him that it’s too late. She refuses to accept his excuses, shoves him away, and walks out. Rosen and the others arrive and arrest her, and the doctor goes inside to help Zelanski. Rachel tells her to stop and that Chris wouldn’t have wanted her to hurt anyone for him.
Later, Rosen and Rachel prepare to leave town. Rosen has told the authorities that Jessica poisoned her victims. Rachel realizes that Jessica is going to Binghamton and Rosen worries that it may be a portent of things to come. She thanks Rosen for his help but he tells her that it was her own ability that saved her life. Rosen assures her that she’s more capable than she knows and suggests that they go home. Rachel says that home sounds good and they depart.