British bombers leave the plant on trial flights, the planes and their young test pilots never to be seen again; accident or espionage? Everyone's a spy of one sort or another in this fast-talking comedy-thriller. “A delightful pre-Bond tongue-in-cheek spy melodrama, serving the useful propagandist purpose at the time of combating war scares and underlining Britain's apparent security and invincibility. Both Laurence Olivier (as the test-pilot hero) and Ralph Richardson as a secret service man let down their hair and play in magnificently relaxed fashion; Richardson's richly comic performance and superb timing is a joy to behold, and the film as a whole, never given its due, is a thoroughly entertaining frolic. Valerie Hobson once again proves that, with the right part and dialogue, she was Britain's Myrna Loy” (William K. Everson).