Deadly Shoals (Wiki Coffin Mysteries)

A New England whaler shows up, desperate to find the devious trader who has cheated him of a thousand dollars and a schooner. Wiki is assigned to find the missing ship, only to follow a trail of clues to a dead body, half-buried in a hill of salt, its skull picked clean by vultures. The adventure unravels in the impoverished village of El Carmen de Patagones, where the threat of French invasion is imminent, and business is at a standstill under the orders of General de Rosas, the tyrant of Buenos Aires.
Wiki must risk both life and reputation in pursuit of a vicious and determined killer who has set his sights on another target: the U.S. Exploring Expedition itself.