Shortly after Paris is liberated, both Billy Boyle and Kaz are in a convalescent hospital - Kaz from having a heart condition and Boyle for exhaustion and excessive drug use. That is when they hear that Boyle's love, Diana Seaton, has been sent to a Nazi concentration camp and Kaz's sister, working with the Polish underground, has been captured. Complicating their desire to go help is a need to solve a murder of a British intelligence officer in the same hospital.