At the height of the American War of Independence, Hart Purchis, captain of a privateer, marries the rebellious spy Mercy Phillips, rescuing her from the wrath of the British in Savannah. But it is not long before the wide waters of the Atlantic separate the lovers: Hart's ship is captured by the British and Hart himself falls under the spell of his evil cousin Julia in London.

Mercy, it seems to him, is lost to him forever. Or is she? Back in Philadelphia Mercy has met a mysterious but charming young Frenchman and is now laying her own plans…