| Director | Anthony Asquith |
|---|---|
| Runtime | 86 min |
| Country | United Kingdom |
At "Port Amberley", a secret aviation research station somewhere in England, a group of scientists are working on the prototype of a revolutionary new aircraft, a supersonic nuclear-augmented jet aircraft code-named M7, taking off and landing on water and capable of flying at up to 2,000 miles per hour. The project is intended to lead to M8, a spacecraft to explore space.
The atmosphere at the laboratory is competitive rather than co-operative, with rivalry between the various scientists. The project leader Michael Heathley is so wrapped up with the M7 that his wife Lydia feels neglected and that she is being sidelined in favour of her husband's work. At a social gathering, she strikes up a conversation with Michael's colleague Alex Leon, and the pair are soon circling one another.
Meanwhile, Michael is desperate to test the M7, but is over-ruled by facility director Carrington. The M7 is finally given its first test flight, and a perilous situation is only just survived. The group continue to work on modifications to iron out minor problems identified on the test flight. Matters take a sinister turn when Carrington dies after an accident. Meanwhile, the project's security members strongly suspect there is a spy in their midst and deploy agents to follow the scientists when away from the station.
The finished version of the M7 then takes to the sky, along with the spy who has talked his way on board. The spy tries to hijack the aircraft, but is foiled by pilot Michael Heathley.