Foyle, now working for British Intelligence, is drawn into the world of corrupt Nazi businessmen when a London university professor is found murdered.

When his colleague Hilda Pierce is nearly killed in an attempted assassination, Foyle must re-examine her top secret role during the war to find out if there was a traitor at the heart of the Special Operations Executive.

Tasked with ensuring security at a high level Palestinian conference, with signs that a plot to bomb the conference maybe under way, Foyle faces a race against time to uncover not only the truth, but where the truth lies. Meanwhile Sam is determined to help a young boy in Adam’s constituency when she realises his life may be in danger because he cannot afford hospital care.

October 1944. Foyle hones in on two murders: an unpopular psychiatrist in a trauma facility and a low security German POW on work release to a local farm.

A.C. Rose orders Foyle to delegate his investigation of black marketing ring and personally look into the possibly seditious acts of a Socialist activist.

American troops arrive in Britain and the Corps of Engineers building an airstrip on a Hastings farm is met with resentment.

The German wife of a rich and influential aristocrat exempted from wartime internment is found decapitated in the midst of anti-German feeling.

April 1944. Milner is unhappy with his new DCS and has asked for a transfer, but after he is murdered, Foyle comes out of retirement to replace him.

Foyle investigates the suicide of a pacifist and death threats to the judge who ruled against his conscientious objector status.

Foyle investigates a man found with a knife in his stomach in a bombed out building while son Andrew gets involved in a top secret radar program.

The apparently accidental death of a young woman in a munitions factory becomes linked with the murder of Milner's estranged wife as he falls under suspicion.

It's June 1945 and Detective Chief Superintendent Foyle is still on duty as they are unable to find a replacement for him. He's approached by Brigadier Timothy Wilson, his former commanding officer from his own military service in World War I, who is looking for a Russian POW, Ivan Spiakov, who has escaped and is believed to have been seen in the Hastings area.

Foyle is now working in a different new role working for British Secret Intelligence. As the iron curtain falls across Europe, MI5 believe that British atomic research has been infiltrated, and ask Foyle to investigate whether a Russian spy network could be at work in London.

With the English army trapped in France and a German invasion imminent, a Nazi sympathizer is murdered during a pro-Facist meeting at a country hotel.

Foyle's investigation of the death of a young black marketeer and stolen food is interrupted by his suspension on charges of sedition.

February 1941: Foyle again pursues a position that would allow him to contribute more to the war effort. But a local murder investigation sidetracks this endeavor as Foyle finds himself caught between rival spy organizations.

April 1941: Foyle questions three Land Army girls about a murder that occurs on a Hastings farm.

Sam volunteers to go undercover to discover how rationed gasoline is being stolen from a fuel depot, and Andrew becomes a suspect in a murder case.

When a British food corporation signs a secret agreement with the Nazis to provide essential food services to the enemy during wartime, murders result.

February 1941: When a local manor house is commandeered for use as a special burn unit for treating injured RAF pilots, Foyle is called in to investigate a series of strange accidents.

August 1942. Foyle investigates the a mysterious disease affecting local farm animals and looks into the arrest of a pacifist accused of stabbing a war hero.

Foyle has his hands full dealing with illegal gambling, sabotage, and his needy goddaughter who shows up on his doorstep with her traumatized son.

July 1945. Sam moves in with Adam Wainwright to help run his guest house though, due to his shyness, they are not a couple. One of the tenants, Mandy Dean, is having a tough time, raising a baby fathered by black G.I. Gabe Kelly. Her old boyfriend Tommy Duggan is devastated when he returns and makes the discovery.

After Foyle is a guest at a friend's home at a dinner for an important American diplomat, a suicide victim and German agent both are discovered near the house.

August 1945. DCS Foyle is replaced and is free at last - he's resigned his position and planning to travel to the United States for an extended tour. Before departing however, he's asked to look into the case of James Devereaux, a young man who joined the Nazi British Free Corps during the war.