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, a mysterious accident claims the life of one of the scientists. Debate arises over the safety of the flight—some advocate for a ground-controlled approach, while Michael Heathley (James Donald) insists on piloting the jet himself. Personal and professional tensions escalate when a colleague, taking advantage of Heathley's distance from his wife Lydia (Phyllis Calvert), attempts to woo her. Additionally, suspicions surface about the presence of an enemy agent within the project. Single-minded and determined, Heathley ultimately uncovers the traitor among them when choosing his co-pilot. Cast: - James Donald as Michael Heathley - Phyllis Calvert as Lydia Heathley - Robert Beatty as Sam Seagram - Herbert Lom as Alex Leon - Noel Willman as Dennis Bord - Maurice Denham as Carrington - Muriel Pavlow as Caroline Cartier - Walter Fitzgerald as Sir Charles Craddock - Patric Doonan as Brian Jackson - Marjorie Fielding as Mother Heathley - Herbert Lomas as George Jackson - Cyril Chamberlain as Inspector Carter - Marianne Stone as Maisie Runtime: 86 minutes.