The series finds Foyle probing the death of a magistrate's German wife and investigating a murder at a radar station where his missing son was working on a highly classified operation.
In Series 2, a corpse is found on a beach, an illicit fuel racket is uncovered, a burglary takes place at the headquarters of a multinational company, and a boy's body is found in woods.
Foyle is drawn into the world of espionage, his son becomes a murder suspect, a farmer is murdered, and a crime crackdown leads the detective to a duo with links to a communist agitator.
The series begins with American GIs arriving in Hastings to a mixed welcome, and ends with a local woman being killed when an experiment in biological warfare goes tragically wrong.
In Series 5, a woman is killed in an explosion in a munitions factory, and the death of a local man found near a military centre leads Foyle into the top-secret world of weapons research.
When an RAF officer is found hanged in a wood, the new chief superintendent quickly rules out suicide, and a murder at a military psychiatric hospital produces no shortage of suspects.
Foyle stumbles on an international cover-up involving the War Office, racial tensions erupt when a black GI is suspected of murder, and a man is sentenced to hang for high treason.