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.

A strange illness threatens the life of three people on the Great Barrier Reef when an old scientist loses control of dangerous research into the effects of radiation on the cycle of marine life.

When sharks come streaking to the scene a diver is in great peril. A wealthy fisherman hunts for a world record size shark, and baits an area with bloody meat. One of the Minus Five divers becomes trapped by a thrashing shark pack attracted by the bait.