At the time of her birth, the Second House of Men had settled in Thargelion, in East Beleriand, living in separate homesteads and having no lords of their own. But in Y.S. 375 of the First Age Morgoth sent out an Orc-raid against them. The Men were caught off-guard, and a great part of their people was wiped out. The remnant was gathered under one Haldad and his twin children, daughter Haleth and son Haldar; and they held out for days in a stockade until the Noldor rescued them, by which time both Haldad and Haldar were slain.
Caranthir offered to Men his lands to live in protected, but Haleth refused, for now she was chosen a Chieftain, being of great heart and no less in valour than her kinsmen. Next year she led her people to Estolad; and after a time again urged them to move further westward. They passed through the horrors of Nan Dungortheb only by the strength of Haleth's will, and at last came to the woods of Talath Dirnen. Later many removed the forest of Brethil, which was a part of Doriath outside the Girdle of Melian, but now was granted to them by Thingol.
Haleth ruled the Folk of Brethil until she died. She was buried in a green mound in the heights of the Forest, which was called therefore the Ladybarrow (Haudh-en-Arwen in Sindarin and Tûr Haretha in their own tongue). The next Chieftain of Brethil was her nephew Haldan.