A beautiful young girl from Thursday Island stows away on the Endeavour, claiming that Jack Meuraka has promised to marry her. Hiding the girl from the Captain proves a major problem.

The Minus Five team is commissioned by the Royal Australian Navy to locate and chart a mine field off the Barrier Reef. During the trip, Captain Ted King risks his life to rescue one of his crew trapped in the mine field, while mines are breaking loose from the rusted cables and menacing the ship.