While scuba-diving near shipwrecks off Bermuda, vacationing couple David Sanders and Gail Berke recover a number of artifacts, including an ampoule of amber-colored liquid and a medallion bearing the image of a woman and the letters "S.C.O.P.N." (meaning "Santa Clara, ora pro nobis", for "Saint Clara, pray for us") and a date, 1714. Sanders and Berke seek the advice of lighthouse-keeper and treasure-hunter Romer Treece on the origin of the medallion, who identifies the item as Spanish and takes an interest in the young couple. The ampoule is noticed by the man who had rented diving equipment to Sanders and Berke, which in turn attracts the attention of Henri 'Cloche' Bondurant, a local drug kingpin for whom the shop owner works, who unsuccessfully tries to buy the ampoule and then begins to terrorize the couple with black magic. The ampoule contains medicinal morphine from the ''Goliath'', a ship that sank during World War II with a cargo of munitions and medical supplies. The wreck of the ''Goliath'' is considered dangerous and is posted as off-limits to divers due to the danger of explosions. Treece concludes that a recent storm has exposed her cargo of morphine and unearthed a much older wreck containing Spanish treasure.