An honest marshal in a corrupt mining colony on Io, Jupiter's sunless third moon, is determined to confront a violent drug ring even though it may cost him his life. After his wife angrily deserts him, he waits alone for the arrival of killers hired by the company to eliminate him. A federal marshal stationed at a mining colony on the Jupiter moon of Io uncovers a drug-smuggling conspiracy. He gets no help from the workers or authorities when he finds himself marked for murder.