The arrest of a young girl on a sabotage charge brings Foyle into contact with a group of English Nazi sympathizers. Shots are fired at the group's charismatic leader, but it is the hotel owner who dies. Foyle investigates the murder and uncovers a plot to smuggle a vitally important letter to the enemy.

In the course of investigating a murder, Foyle uncovers a plot to steal art treasures being moved from the local museum to Wales for safekeeping. Meanwhile, Foyle's son flies his first mission as a Royal Air Force pilot and is accused of passing top secret information to the enemy.

October 1940. At the London headquarters of a multinational company, a young secretary plummets to her death. In Hastings, a member of the Home Guard is killed. Foyle and Milner discover how these deaths are linked and how money talks a universal language, even in wartime.

September 1940. Sam's boarding house is bombed and valuables disappear, alerting Foyle to an organized ring of looters. After the father of one of the suspected looters is found dead on the beach, Foyle and Milner's investigation leads them into conflict with British efforts to secure the donation of American Aid and the crucial start of Lend-Lease in the war.

Investigating a suspicious death, Foyle gets caught up in the rivalry between the established spy agency MI5 and the newly created SOE.

April 1941. Foyle and Milner capture two German soldiers who survive the crash landing of their plane in the Hastings countryside. Nearby, two nights later, a farmer is discovered shot dead in his armchair. Two Land Army girls working on the farm come under suspicion.

April 1942. Cultures clash as the first Americans arrive to build an airfield near Hastings. Some locals see the "invaders" as a threat. Others find the chance for romance among the young Gis. But when a barmaid turns up strangled. Foyle's investigation strains British-American relations to the breaking point.

March 1943. While investigating a gambling ring and incidents of sabotage, Foyle becomes distracted by a personal crisis. His troubled goddaughter, Lydia, shows up unexpectedly at his doorstep-along with her young son James, a boy so deeply traumatized by a bomb strike at his school that he refuses to speak.

May 1945. As all of Britain awaits the formal announcement of the war's end, Foyle reluctantly joins a committee preparing to keep public order during the celebration to come. But the end comes too soon for two men-one a stabbing victim, the other an apparent suicide.

October 1944. At a psychiatric clinic treating troubled soldiers, the investigation of a doctor's murder turns up no shortage of suspects among the patients and staff. It also complicates Foyle's friendship with Dr. Josef Novak, the Polish refugee who heads the clinic.