After a German plane crash lands in the Hastings countryside, Foyle and Milner capture two airmen, Sabartovski and Schimmel. They are handed over to Major Cornwall, who works for the POW interrogation service.
Nearby on Hugh Jackson's farm, a brand new tractor has been delivered, to the delight of the land girls, Rose and Joan, but rival farmer Curling is bitterly jealous. Jackson's son Tom and the girls are up to something but keep their activities secret from Barbara, a Polish defector staying at the farm.
The next morning, Jackson is discovered shot dead in his armchair. Another German, Weiser, is found nearby, his parachute caught in a tree. His pistol is missing, but before Foyle and Milner have a chance to interview him, Cornwall takes him away.
Foyle discovers a bra in Jackson's bedroom. It is found to be Barbara's but everyone at the farm is a murder suspect. Foyle also learns that Tom's mother ran away with a farm hand, Andrew Neame, when he was a child. Keen to do her bit to help the war effort, and perhaps find out some inside information, Sam goes to work at the farm.
At the POW camp, Schimmel seems concerned that Weiser will soon be well enough to leave the sanatorium. A Luger pistol is found at the farm and Weiser tells Foyle that a woman matching Barbara's description took it while he was stuck in the tree.
Foyle questions Barbara in the woods while Milner finds a pig in a freshly dug grave. They also encounter a mysterious man whom Foyle guesses is Neame. Rose and Joan are arrested in connection with meat profiteering and Rose admits she is pregnant with Hugh Jackson's child. Meanwhile Schimmel and Sabartovski are caught trying to escape from the camp.
Neame denies running away with Mrs Jackson, but where is she? Can Sam find the answer at the farm? And can Foyle and Milner discover the truth about the German prisoners of war before it is too late?