Major Hammond of Scotland Yard (Ralph Richardson) is called in to investigate the mysterious disappearance of prototype British aeroplanes when on their test flights. At first Hammond is seen as an outsider at the factory but he soon finds a friend in star pilot Tony McVane (Laurence Olivier) who helps him try to unravel the case. Hammond becomes convinced that the company secretary at the factory Jenkins (George Curzon) is a foreign agent and follows him to London. Meanwhile, the mystery still remains unsolved when Tony returns to the aircraft factory determined to make the next test flight. His aircraft is brought down by a powerful ray beamed from a mysterious salvage ship. Tony is taken hostage on the ship, where he discovers many other missing pilots have suffered the same fate. Will Hammond come to McVane's rescue and save the day?