. The humans died long ago after an acid rain storm. Some lucky humans made it underground- but they can never come back up. The storm isn't quite finished; acid rain falls from the sky every day. A new species that can endure the harsh conditions, 'scavengers', have taken their place. After being sent out to find food, a scavenger named Tor gets distracted- as usual- by a dead robot laying against a wall in the old abandoned city. Tor fixes up the robot, expecting it to just be some machine they can keep in their storage. As Tor learns the robot's mysterious past, everything changes. .