In the future, humans try to escape global destruction by moving underground.

In the distant future, mankind begin research on clones that live underground in search of lost genetic information.

Mankind can no longer reproduce because of gene manipulation aimed at making life longer. The clones ruling the bottomless underworld may have become fertile. Parton is selected to go on a mission through a subterranean labyrinth crawling with monsters to secure humanity's future.

1,042 years before JUNK HEAD, a robot named Robin escorts a human commander on a mission to the underground city of Carp Bar.