First, a fishing trawler runs aground on the Massachusetts shore. Then, a young scuba diver sent to investigate the wreck is found floating lifeless in the water. Doc Adams, the unhappy friend of the unlucky aquarian, has just been launched through the stormy seas and blood-flecked sands of the Cape Cod coast to plumb the depths of a murder he should have prevented. There he uncovers a hidden treasure in illegal arms and barely survives a near-fatal confrontation with a gun. That leaves the killers he's hunting with the comfortable feeling that Doc is dead.

Now Doc can watch for the first wrong move they make...