fom: http://www.thebricktestament.com
After leaving Zoar, Lot settled in the hill country with his two daughters, for he dared not stay at Zoar. He lived in a cave, he and his two daughters.
The elder said to the younger, Our father is an old man, and there is no one here to marry us in the normal way of the world. Come on, let us ply our father with wine and sleep with him. In this way we can preserve the race by our father.
The next day the elder said to the younger, Last night, I was the one who slept with our father. Let us make him drunk again tonight, and you go sleep with him. In this way we can preserve the race by our father.