Sir Ernest Pease is a self-important scientist sent undercover on a bombing mission to monitor the effectiveness of his latest invention, a new-fangled radar. When the plane is attacked, he parachutes to safety — only to be sent to a POW camp, where he takes on the alias of Lieutenant Farrow. There, the somewhat happy-go-lucky bunch of Brits suspect their acerbic new fellow prisoner of being a spy, and all sorts of culture clashes and misunderstandings ensue.