In 1942 a Japanese invasion of Australia was thought to be imminent; panic decisions were made to conceal arms and some gold bullion, ready for the use of an underground resistance force. An army officer and his sergeant were dispatched to establish a hidden cache at the Myall Lakes but were both killed before they were able to report its hidden position. Many years later, the cache was discovered by an international crook while on holiday. He decided to use an old wartime submarine to remove the gold and a British army officer is sent to aid the local police to foil the criminal's plans.