Raoul Leduc is a police inspector trailing a spy who plots to kidnap an important American atomic scientist. Joe Victor a gangster who is hired to carry out the abduction, balks when he learns what is at stake and helps Leduc out instead.

In 1941 Greece, on the eve of German occupation, cynical American foreign correspondent Michael Morrison arrives in Athens, intending to depart for London the following day. While there he is tricked into smuggling a list of resistance leaders out of the country and is pursued by the Germans.

Mike and Tony Petrakis are a Greek father and son team who dive for sponges off the coast of Florida. After they are robbed by crooks, Arnold and the Rhys brothers, Mike decides to take his men to the dangerous 12-mile reef to dive for more sponges. Mike suffers a fatal accident when he falls from the reef leaving Tony to carry on the business. But now he has a companion, Gwyneth Rhys.