Sag Harbor, New York, 1840s: Catherine McGuirk leaves Ireland and a shipboard proposal behind, determined to forge a new life in America. Amid the bustling height of the whaling era, she marries a dashing sailor who vows to give up life on the sea. But when he vanishes westward in pursuit of gold, she is forced to chart her own course as a governess in Manhattan society. Torn between her ambition, the vanished whaleman she married, and the now-wealthy suitor she refused, Catherine must navigate love, loss, and the tides of a changing world.