There is tiny chance, measured in the tenths of a percent, that an asteroid with a trajectory coinciding with Earth's, strikes us within the next two decades.
This is an alternative future in which an asteroid with a diameter over 30 km crashes into the Earth, before the year 2020.
This scenario predicts the state of our world after the cataclysm. It is a work of fiction; to make it more enticing and believable, characters, organisations and locations are given proper names.
Optimistic forecasters beware: this is a thoroughly pessimistic vision of a bleak future. Dates begin from Year 1 A.C, After Cataclysm.
Earth is hit by a large asteroid. (This is a Point of Divergence.) An immense shockwave rips through the surface of our planet. Dark clouds blacken the sky, covering the globe. (Remember how in Tolkien's Lord of the Rings trilogy, a blackness permeates the firmament and darkens the sky as far as the eye can see?) This is Earth, Year 1 A.C.