Billy is sent to London in the midst of the Luftwaffe bombing offensive to investigate the murder of a Soviet official. There's reason to believe that the crime could be connected to the recent discovery of mass graves in the Katyn Forest, where thousands of Polish officers were executed. If the killer is out there, the diplomatic stakes are high as an uneasy relationship between the Soviets and allied powers hangs in the balance. Further still, Scotland Yard names Billy's friend Kaz as the prime suspect. He must track the killer through London's underworld.