Thirty-nine women and a girl are being held prisoner in a cage underground. The guards are all male, and never speak to them. The girl is the only one of the prisoners who has no memory of the outside world; none of them know why they are being held prisoner, or why there is one child among thirty-nine adults. One day, an alarm sounds, and the guards flee; the prisoners are subsequently able to escape. They find themselves on an immense barren plain, with no other people anywhere, and no clue as to what has happened to the world.