It is 1702, and in the lawless Caribbean sea young Matthew Loftus determines to captain his ship by honest trade rather than piracy and plunder. But his crew lust after the spoils that the fast, well-armed Cornelius can win, and even his love, Abigail, doubts him. Encountering an old man who chants endless numbers and incantations, he learns of a secret almanac that advances the science of navigation. To redeem himself, Matthew embarks on the cause of solving the Longitude, the lack of which wrecks hundreds of ships and drowns thousands of seamen. But is it almanac what is seams? Can it really give a position fix at sea by sighting the moon against the stars? Pursued by unprincipled merchants, duplicitous privateers and the English Navy through the battles on the high seas and sinister perils on deserted tropical shores, Matthew struggles not only with navigational uncertainties but also with the venal motives fuelling commerce and war in the Caribbean. The passage is strewn with the reefs and shoals of treachery and falsehood, and beset by clashing currents of political trickery, patronage and ambition. Despite loss and in justice, through gales and sea battles, he sails his beloved schooner towards the great goal he has set himself.