When Peter’s family moves back to London after ten years living abroad, all the 13-year-old wants to do is to settle down and make friends. However, Peter’s world is turned upside down when he explores a London mansion that was once a Russian embassy. He discovers an old Russian hiding out in the mansion. Illya Grigorevich is being retired and sent back to Moscow. But Illya refuses to go. During the 1960s, Harry Grebb, now German Ambassador to Britain, abducted and murdered Illya’s best friend, Dimitri Denisovich. Grebb accused Dimitri, who was known as DD, of being a double agent. But Grebb’s motive was that he and DD were love rivals for the same woman. Now Illya wants to expose Harry Grebb for the murder of his friend DD. But Grebb sets out to silence Illya. Peter’s parents want to send him away to boarding school. Peter refuses to go. Illya leaves England to get away from Grebb. Peter persuades Illya to take him with him. But Grebb gives chase. Peter and Illya run for their lives to Paris and then on to Geneva in Switzerland, with Grebb close behind. But Illya has a surprise up his sleeve for the unsuspecting Grebb.