Alan Saul is now part human and part machine, and our solar system isn't big enough to hold him. He craves the stars, but can't leave yet. His sister Var is trapped on Mars, on the wrong side of a rebellion, and Saul's human side won't let her die. He must leave Argus Station to stage a dangerous rescue -- but mutiny is brewing on board, as Saul's robots make his crew feel increasingly redundant.