A secret jet aircraft capable of traveling three times the speed of sound is being developed by a group of scientists. On the day of the test flight, one of the scientists dies in a mysterious accident, and there are many arguments concerning the flight itself; some think it should be ground-controlled while Heathley (James Donald) wants it to be a manned flight with himself at the controls. Conflict also arises when one of his fellow scientists, taking advantage of Heathley's lack of attention toward his wife, Lydia (Phyllis Calvert), makes some moves on her. Then there is the question of just who is the enemy agent on the project.
Practical Effects
Genuine Saunders-Roe flying boat footage looks expensive
Acting
Herbert Lom brings slimeball energy to every scene

Director
Anthony Asquith
Trivia, insights & behind the scenes
The flying boat sequences feature the real Saunders-Roe SR.A/1, an actual jet-powered seaplane fighter that never entered production — making this inadvertently precious aviation documentation.
Released during the early Cold War and Britain's anxious decline as aerospace leader, the film's desperate cheerleading for British technological supremacy now reads as melancholy propaganda.