Dr. Holt continues to lose control of his hand due to the stress he is under at the hospital and his lack of sleep. His hand continuously tries to murder Chanel while they're on dates, leading Chanel to break up with him.
Dean Munsch volunteers Brock to perform an incredibly complex and risky surgery (the separation of subsumed conjoined twin limbs and a heart transplant) for new patient Anna Plaisance. Brock, unable to control the hand, attempts to back out of the surgery. Munsch, who is punishing Brock for choosing Chanel over her, refuses to allow him to back out of the surgery and calls in a medical journalist named Slade to watch and document the surgery so that the hospital will have an influx of good press.
Meanwhile, using psych questions and questions from Cosmo quizzes, Chanels #3 and #5 manage to deduce that Cassidy Cascade is (1) not dead and (2) the Green Meanie killer. #3 doesn't want to turn him in because she's falling for him and bribes #5 with candy to keep quiet about it. Hoffel overhears that the Chanels (and Hester) know that Cassidy is a killer and that Brock's hand is attempting to kill Chanel.
Brock attempts to cut his hand off but is unable to. They're interrupted by a Green Meanie attack and the evil hand, which knows martial arts, saves him.
Hoffel aims to hack Brock's computer in order to push his hand over the edge so that he'll kill Chanel for Hoffel. She also instructs Cassidy to kill #3 next. Cassidy refuses, in love with her, but Hoffel threatens to turn him into the police if he doesn't comply.
#3 and Cassidy work on their own case, where a man with a loving and devoted girlfriend seems to be poisoned by dioxin, a powerful toxin. The girlfriend refuses to leave her boyfriend's side, warming #3's heart and making her believe in true love. This encourages #3 to tell Cassidy that she knows he's a killer but that she loves him and won't turn him in. Simultaneously, Cassidy tells #3 that he loves her too and that he won't kill her but will have to kill Chanel.
While investigating the man's poisoning, Cassidy and #3 at first believe the girlfriend has Munchausen by proxy syndrome and is poisoning her boyfriend. It turns out that the man is poisoning himself, tired of his girlfriend and trying to get her to leave him by making himself really sick and unattractive. This jars #3, who reconsiders turning Cassidy into the police because true love might not exist after all. In response, Cassidy says he might just kill #3 in that case.
One of the Chanels (the one with the extra feet of intestines) is attacked by one of the Green Meanies the night before Anna Plaisance's risky surgery. She's left braindead but alive. Hoffel and Munsch talk to Brock about pulling the plug on #10 since she's a donor. Brock is uneasy about the convenience of a viable heart showing up right before the surgery.
Brock manages to perform the surgery on Anna Plaisance (with Cassidy assisting) successfully with his evil hand tied behind his back, under the watchful eyes of Dean Munsch and the journalist Slade. The Chanels assist in the surgery by calming Brock down by singing "99 Red Balloons." Brock and Chanel embrace and make up.
#3 and Cassidy prescribe a fix for their patient's self-inflicted dioxin poisoning. Cassidy reconsiders killing #3. He vows to #3 that he won't kill her or Chanel (as #3 requested of him earlier) and that he'll do what he can to make sure they aren't killed. This tips #3 off that there is another killer out there, but Cassidy is unable to rat out Hoffel to #3.
Cassidy offers to perform the surgery to replace Brock's evil hand with one of the conjoined twin hands Brock removed from Anna Plaisance. Brock happily agrees.
Slade goes down into the hospital's basement to phone someone named Arthur to come down to the hospital because he has seen many ethical violations there over the past two days. Slade sees Denise in the cryogenic freezing chamber but is then murdered himself by one of the Green Meanies.
That night, Brock and Chanel are sleeping together in bed. While asleep, Brock's evil hand writes "Kill Chanel" on a piece of paper on the nightstand.