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.

August 1942. Helping a colleague from a nearby town probe the murder of a war hero, Foyle confronts a deeper - and potentially deadlier - mystery. A top-secret experiment in biological warfare goes horribly wrong, claiming the victim's widow and threatening the life of Foyle's driver.