Kill for Me, Kill for You

After six-year-old Jess White is murdered, Amanda White's husband Luis dies by suicide a week later. Amanda becomes convinced that registered sex offender Wallace Crone killed Jess. After Crone's murder charge is dismissed and Amanda later violates a restraining order while confronting him, court-ordered counseling brings her into a trauma group where a woman using the name Wendy befriends her and later says her real name is Naomi Cotton. Naomi claims Frank Quinn abused and killed her daughter and proposes a murder exchange: she will kill Crone if Amanda kills Quinn. Naomi soon tells Amanda that Crone is dead. Amanda goes to Quinn's home but realizes she cannot kill a stranger in cold blood. Quinn attacks her, and she seriously injures him while defending herself and escaping. She later sees Crone alive and realizes Naomi lied.

Interleaved chapters follow Ruth Gelman beginning in 2007, when a blue-eyed intruder attacks her at home. Ruth later becomes convinced that hotel guest Patrick Travers is the attacker, and her husband Scott kills Travers during a confrontation. Travel records then prove Travers could not have attacked Ruth. As Ruth's fear and misidentifications intensify, Scott confesses to the killing and jumps from a window. Ruth is later found not guilty by reason of temporary insanity, spends seven years at Kirby Forensic Psychiatric Center, and is released. In the present, she uses multiple false identities, phones, and support groups to recruit grieving people into murder exchanges aimed at men who resemble the original attacker. Naomi Cotton is one of those identities.

Amanda's attempt to learn who Naomi really is eventually brings her together with Billy Cameron, who claims that a woman using the name Felicia Silver tried to recruit him to kill Quinn and that his wife Lucille was murdered. Amanda and Billy connect Felicia and Naomi to the same woman, identify her as Ruth, and find a pattern of men resembling Ruth's attacker who were killed after murder-swap arrangements. With help from Dr. Marin and Scott's old friend Jack, they obtain recent false identities used by Ruth and trace her to a Brooklyn rental. Ruth, meanwhile, becomes convinced that Mr. Granger is the blue-eyed attacker and decides to kill the Granger family herself. She attacks concierge Raymond at George Towers and goes to the tenth floor with a gun. Amanda and Billy follow her there as Dr. Marin, Farrow, and Hernandez converge on the building.

Billy reaches Ruth first. He identifies himself as BillyCam2003, an online contact she once considered recruiting, removes brown contact lenses to reveal blue eyes, and confirms that he is the man who attacked her years earlier. Billy says he tracked Ruth after recognizing that men who resembled him were being killed and concluded that she might eventually target him. Ruth fires at him and misses when the elevator gate knocks the gun from her hand. Before Dr. Marin arrives, Billy puts brown contact lenses back over his eyes. Marin therefore sees Ruth accusing a brown-eyed Billy of being her attacker, interprets the accusation as a recurrence of her earlier paranoid behavior, and sedates her.

Two months later, Farrow confronts Amanda with degraded blood from Quinn's property that produced a partial DNA match to her, but he indicates that he may let Quinn's homicide remain unsolved. He tells her Ruth is awaiting trial for the attack on Raymond, attempted murder charges involving the Grangers, and fraud, and that police may not connect her to every murder. Farrow also tells Amanda that Crone has been found stripped, tortured, and killed. A letter from Billy then reveals that Lucille never existed, that he already knew Ruth's identity before meeting Amanda, and that he used Amanda as a buffer between himself and police and as someone Dr. Marin would trust. Billy says Crone confessed to killing Jess before he died. Amanda burns Billy's letter and Jess's toy unicorn Sparkles on the Coney Island beach, ending the novel feeling neither afraid nor alone.