Karl Ehrlich (John Wayne) is the German captain of a freighter stationed in an Australian port. Ehrlich, a fervent opponent of Nazism, receives word that World War II has commenced in Europe, and that he must immediately make his way to Germany while avoiding the pursuing Allied ships. Aboard his ship is a German spy (Lana Turner), whose safe passage he must ensure. Meanwhile, a British ship — with Cmdr. Jeff Napier (David Farrar) at its helm — is hot on their trail.