The year is 1643. Roberto, a young nobleman, survives war, the Bastille, exile and shipwreck as he voyages to a Pacific island straddling the date meridian. There he waits now, alone on the mysteriously deserted Daphne, separated by treacherous reefs from the island beyond: the island of the day before.

If he could reach it, time - and his misfortunes - might be reversed. But first he must learn to swim...