At the request of MI6 agent John Crawley, Alex becomes a ball boy at Wimbledon. There, he finds that the Chinese Triad gang "Big Circle" is fixing matches. He foils the plot, but soon becomes a target and barely survives an attempt on his life while surfing on vacation with a friend, Sabina Pleasure. For his safety, both MI6 and the CIA send him with CIA agents Tom Turner (Glen Carver in the US version) and Belinda Troy to the Cuban island of "Cayo Esqueleto" (Spanish for "Skeleton Key") to investigate General Alexei Sarov. Alex learns that Sarov recently purchased nuclear material, and the CIA is concerned about what will happen next.
To enter Sarov's mansion, Turner and Troy go scuba diving. When they do not return, Alex dives as well and, after a close encounter with a shark, discovers a mechanical spear trap that impaled Turner and Troy. When he resurfaces, the boat driver has been killed and Alex is captured by Sarov's henchman, Conrad. Sarov tells Alex that he plans to detonate the nuclear bomb at Murmansk (Мурманск in Russian), in an abandoned shipyard of nuclear submarines. The nuclear fallout will force President of Russia Boris Kiriyenko out of power and lead to Russia reclaiming glory lost during the dissolution of the Soviet Union. Sarov also wishes to adopt Alex as his son, as he reminds Sarov of his own son who was killed in action in Afghanistan whilst serving in the Soviet army.
When the plane they are traveling in stops at Edinburgh Airport, Alex uses a stun grenade (courtesy of Smithers at MI6) to distract Conrad, and escapes the plane. A security guard named John Prescott, however, grabs Alex's phone as he tries to call the police. Sarov quickly recaptures Alex and kills Prescott. At Murmansk, Sarov plants the bomb and ties Alex up due to his earlier escape attempt. Alex escapes; Conrad tries to kill him, but Alex avoids Conrad and kills him with a giant magnetic crane used to lift the bomb. (Conrad had numerous pieces of metal inside his body, which were powerfully attracted to the magnet.) He then removes the detonation card from the bomb. The Russian army arrives and starts fighting Sarov's men. When Alex tells Sarov that he would rather die than become Sarov's son, Sarov commits suicide.
In the final chapter of the novel, it is told that when Alex explained his predicament to John Prescott, his office heard their conversation through Prescott's radio transmitter. Initially, they didn't believe Alex, but when they discovered Prescott's death, they immediately notified MI6, who then warned the Russians. Alex is depressed after having seen Sarov shoot himself, but Sabina visits Alex and invites him on holiday with her family in France for a couple of weeks, cheering Alex up.