1896: four Englishmen flee for their lives across the Kalahari Desert, carrying a stolen fortune in raw diamonds. The thieves manage to reach the waiting HMS Rove - only to die with their pursuers in a vicious storm. Present day: Juan Cabrillo and the crew of the covert combat ship Oregon intercept a mayday from a boat under fire off the African coast. They save the beautiful Sloane Macintyre, who's looking for a long-submerged ship that may hold a fortune in diamonds. She tells a surprising story about a crazy fisherman who claims to have been attacked by giant metal snakes. What begins as a snake hunt leads Cabrillo on to the trail of a far more lethal quarry . . .