In Greek mythology, Theseus forgot to change his ship’s black sails before returning to Athens.
Theseus’s father, Aegeus, had instructed him to replace the black sails with white ones if the expedition to Crete ended successfully. The color change would have signaled from a distance that Theseus was alive. After defeating the Minotaur and escaping Crete, Theseus’s ship returned with the black sails still raised.
Aegeus saw the ship approaching from the coast and believed his son had died. In the best-known version of the myth, he threw himself into the sea, which was subsequently called the Aegean Sea. Some ancient accounts vary in details, but the failure to change the sails is the standard explanation for Aegeus’s death.