A wreck with a cargo of whisky hangs precariously on a ledge on the Reef. A puritan Scotsman plans to destroy the cargo, and a drunken beachcomber warns the Minus Five team, who are working to retrieve a new navigational aid from the wreck. The navigational aid must be assessed, for if it is defective it could endanger the other five ships it has been issued to, but their work is hampered by the old Scotsman who is determined to destroy the whisky before it can cause any evil.
 

A Japanese submarine sunk during World War 2; a Shinto burial service; and the unusual interest displayed by a Member of Parliament plunge the Minus Five team into a new mystery on the Barrier Reef.