Gene Kelly stars in a tense dramatic role as an American scientist sent to work with a team of British sailors on a remote Scottish island. He must prove his worth to the resentful British while testing a highly dangerous new torpedo.

The scene is Brighton, with holiday makers awaiting the arrival of Kolley Kibber, who is working on a stunt for his newspaper. A gang, led by Pinkie Brown, recognize Kibber as the man indirectly responsible for the death of a former gang leader. Kibber, recognizing the vicious young Pinkie, fears his life is in danger. He is right: his body is later washed ashore. Spicer, one of the gang, ensures an alibi by leaving Kibber's cards at various places. But he gets an attack of nerves, and Pinkie arranges for a rival gang to eliminate him.