God is planning to flood the world, but he doesn't want this to be the end, he wants to make sure that it can be re-populated when the floodwaters recede. So he calls on Noah and tells him to build a boat, a boat big enough to carry two members - one male, one female - of every animal species on earth. Noah complies and when the rains begin, he and his family round up the animals and commence their voyage.
