DS-5, a biologically-enhanced law enforcement marshal, is due to be decommissioned after decades in deep space. He returns to a solar system finally rising out of a devastating climate war following the discovery of a miraculous new energy source: Titan Green. His pod crashes on Titan following a mysterious explosion, and DS-5 deploys for his final mission: an investigation into mass murder that becomes entwined with a geologist's quest for her missing father. But as DS-5's ageing tech begins to fail, human faculties and memories resurface, forcing him to confront the dark provenance of his recruitment.