The fifth installment in the Alex Cross series opens with Geoffrey Shafer, a British Embassy official in Washington, D.C., driving his Jaguar at suicidal speeds through the city before escaping consequences by invoking diplomatic immunity. That night, he messages fellow players in an online role-playing game called the Four Horsemen, in which he plays the character Death. He picks up a teenage prostitute in the Petworth neighborhood, drives her to a park, and stabs her.
Alex Cross, a senior homicide detective and FBI liaison in Washington, is a widower raising two children, Damon and Jannie, with the help of his grandmother, Nana Mama. Cross's first wife, Maria, was murdered in an unsolved drive-by shooting, a loss that still drives his commitment to solving homicides. He is in a relationship with Christine Johnson, the principal at the Sojourner Truth School.
Cross has been tracking a pattern of unsolved murders in Southeast Washington: women found dead with no identification, left where they might not be found quickly, with no witnesses. His superior, Chief of Detectives George Pittman, refuses to authorize an official investigation. Cross and a small group of detectives, including his partner and childhood best friend, John Sampson, begin meeting at Cross's home to work the cases, nicknaming the unknown killer "the Weasel."
Shafer lives a double life. In the upscale Kalorama neighborhood, he poses as a devoted husband and father to his wife, Lucy, and their children. In secret, he rents an apartment in the Eckington neighborhood, where he keeps a purple and blue gypsy taxicab he calls the "Nightmare Machine." Disguising himself in blackface and padding, he prowls the streets at night selecting victims according to rolls of twenty-sided dice. The game is played online with three other players: Conqueror, Famine, and War. Each player serves as his own gamemaster, crafting fantasies meant to shock the others. Shafer claims his stories are real.
One of Shafer's victims is Nina Childs, a nurse whom both Cross and Sampson knew well. Her murder deepens Cross's determination, and he develops a profile of the killer: an organized male caught in an escalating fantasy cycle, possibly with a decent job and a family. Cross proposes to Christine at the National Cathedral, and she accepts. Shortly after, a naked white man, Franklin Odenkirk, is found shot and dumped with no identification. Odenkirk, a research analyst at the Library of Congress, was sodomized after death, suggesting a single killer operating across racial and class lines. Pittman insists Cross focus only on this high-profile case.
George Bayer, who plays Famine, travels from Asia to Washington and finds the hideaway and taxi, confirming Shafer's claims are real. After Bayer visits two young prostitutes and leaves them unharmed, Shafer follows him there and murders both girls, seventeen-year-old Tori Glover and fourteen-year-old Marion Cardinal. Cross learns that Marion was not a prostitute but had accompanied her friend to protect her.
Cross shares his case files with a Washington Post reporter, prompting a front-page story about racial bias in police investigations. Pittman retaliates by suspending Sampson and other detectives. A witness tells Cross that the girls got into a purple and blue gypsy cab driven by a white man, and Cross begins canvassing the Eckington neighborhood. Shafer discovers the police are closing in and declares Cross a new "player" in the game.
Cross takes his family and Christine on vacation to Bermuda. Christine rides a moped into Hamilton to shop and does not return. Cross receives a message stating that Christine is safe for now and that her captors have her. Cross and Sampson search the island for days. A witness reports seeing a white van deliberately hit a woman on a moped before a man pulled her inside. No further leads emerge, and Cross returns to Washington devastated.
In a significant escalation, Shafer breaks into the home of a prosecutor named Deirdre Cahill in Fredericksburg, Maryland, and murders Cahill and her teenage daughter. For the first time, Shafer has broken the game's rules: His dice roll required him to leave without killing, but he ignores the result.
Detective Patsy Hampton, a young homicide detective whom Pittman assigned to spy on Cross, has been independently investigating the murders. She traces the Four Horsemen game through an online chatroom and identifies Shafer and his position at the British Embassy. Hampton contacts Cross, and the two begin sharing information. At Shafer's hideaway, Cross finds photographs of himself, his family, and Christine taken in Bermuda, linking her abduction to the murders.
A phone call directs Cross to the Farragut, an apartment building where Shafer's therapist, Dr. Elizabeth "Boo" Cassady, lives. Cross finds Hampton murdered in her Jeep in the parking garage. He goes to Cassady's penthouse and finds Shafer with blood on his trousers. Cross arrests him over protests of diplomatic immunity.
The arrest triggers an international controversy. Shafer's defense attorney, Jules Halpern, files a fifty-million-dollar suit against Cross, but Shafer agrees to waive diplomatic immunity and stand trial for first-degree murder. A suppression hearing allows evidence from Shafer's clothing and the garage but bars everything found inside Cassady's apartment.
Cross begins working with Andrew Jones, a senior director from the British Security Service. Jones reveals that all four Horsemen are current or former MI6 agents and that the game originated in Bangkok in 1991. He proposes a partnership: If Cross helps bring down the players, Jones will investigate Christine's disappearance.
The trial becomes a media spectacle. Shafer stages a suicide attempt to generate sympathy, and his defense presents testimony portraying an ideal marriage and an alibi from Dr. Cassady. Halpern cross-examines Cross, exploiting his emotional state and the presence of his fingerprints and Hampton's blood on his clothes. Shafer takes the stand and delivers a soliloquy, addressing the jury directly without examination by his own attorney. He insists on his innocence, and the jury returns a verdict of not guilty. Shafer approaches Cross and says, "You killed her," confirming to Cross that Christine is dead.
Cross continues working with Jones. Shafer, deteriorating at the embassy, proposes a final meeting in Jamaica to end the game. Cross, Sampson, Jones, and teams of detectives set up surveillance at the Jamaica Inn in Ocho Rios.
Shafer arrives by boat. Bayer meets him on shore, apparently sent to kill him, but Shafer breaks his neck. Shafer storms the hotel, shoots two British agents, and executes Oliver Highsmith, the player known as Conqueror. He drives to the beach house of James Whitehead, the player known as War, and shoots him in the spine, deliberately paralyzing him. Shafer reveals his motive: The other Horsemen recruited him as an assassin in Asia, made him into a killer, and he holds them responsible.
Cross chases Shafer into the Caribbean Sea. Shafer attacks underwater, but Cross kicks him under the jaw. Shafer goes limp and sinks. Cross nearly drowns before Sampson rescues him. Shafer's body is not recovered.
As Cross prepares to fly home, Jones rushes to the airport: A local thief has revealed that an American woman has been kept in the hills near Ocho Rios by an outlaw group connected to Whitehead. Cross drives to a remote settlement and enters a small shack. Christine is alive, thinner and with longer hair, holding their newborn son, whom she has named Alex.
In an epilogue set months later, Shafer is alive in London, disguised and using the name Frederick Neuman. He stalks his estranged wife Lucy at a supermarket and slashes her throat, killing her. He disappears, confirming that Death has survived and the game continues.