The Danaids were the fifty daughters of King Danaus. They were betrothed to the fifty sons of the king's brother, but there was no love lost between the two brothers. On orders from King Danaus, all but one of the fifty daughters murdered their new husbands on their wedding night (Hypermnestra was the one exception). As a punishment, the Danaids were condemned for all eternity to try to fill a tub with water.
You can also find more myths and legends for the week of December 4-10 here. For more information and links to the actual javascript code, see the Myths & Legends Widget Reference Page.
