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.

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.

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.

Foyle finds himself being drawn into the strange murder of an ex-Nazi defector and leading expert on Soviet intelligence who had been working for MI5. Sam’s husband, Adam, is pre-occupied with his new political jobleaving her concerned that she’ll be able to share some huge news with him.

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.

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.

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.

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

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

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

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.

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.

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.

Foyle investigates the death of a Russian and it ends up leading to a mysterious military facility run by a Colonel with an impeccable war record.

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.

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