In the half-light of the Gulf of Mexico's false dawn, the salvage boat Sea Devil capsizes and sinks, killing Nick Gallagher, a well-known treasure hunter. When his estranged son Jack, a recently retired navy fighter pilot, comes to Key West for the funeral, he discovers that the sinking may have been no accident.

Amid the torrid, honky-tonk atmosphere of Key West and the volatile weather of the Gulf, Jack Gallagher attempts to find out what happened to his father and why. He confronts a motley group: his father's vindictive ex-partner, Cuban exiles, a Cajun dive master, a venal and pompous politician, a bombastic lawyer, a high-handed archeologist, and a sultry, seductive reporter. As he searches for answers, Gallagher inexorably becomes captured by his father's obsession for the Magdalena treasure: a vast array of gold doubloons, silver ingots, exquisite jewelry, and priceless artifacts lost when a hurricane destroyed the Spanish treasure fleet in 1642.

A second dive accident, a burglary, a courtroom brawl, and another death all lead to the violent climax at the heart of a hurricane in the Gulf. Ultimately, Gallagher finds not only the truth about his father's death, but about his father's life, as well as his own, and about the real treasures in life: loyalty and friendship.