The Minus Five team has salvage rights to a vessel sunk off the Barrier Reef in the 1800's, but when they arrive they find divers down below. The gold disappears and it seems it has been stolen from under their noses. A cannon from the wreck and an old log book must be found before the mystery can be solved.

Tense moments mix with comedy when three students capture the Endeavour and, thinking the crew are spies, plan to hand them over to the police.

Old Harry tells Steve Gabo about two million dollars of gold coin carried on a plane lost during World War 2, which he has been trying to locate for years. The Minus Five team begin a search and find more than they bargained for - two skeletons, and two armed men who could be murderers, but who are in fact Commonwealth Police.