Four hundred years in the past, far from the planet Earth, a couple of intergalactic truckers screw up. The cargo that they were to be delivering--specimens of a bunch of different species--is sent hurtling through space when their hitch comes undone.
On present-day Earth, that intergalactic "Noah's Ark" is coming. Everyone on the ground mistakes it for a meteor. At first, they consider trying to find some defense for the "meteor", but when they later consider its size and trajectory, they figure it will do no harm.
They let it land, only to discover that it's not a meteor at all, and that some of the life-forms inside survive . . .