When a scientific team exploring an obscure planet fails to make its regular communications check, the Marines of the third platoon are sent to investigate. They prepare for a routine rescue operation, but what they find on Society 437 is a horror beyond description. Only a handful of ragtag pirates who were in the wrong place at the very worst time have survived, and there is little trace of the scientists.
What happened to the scientists? Why have the pirates been spared? Gunnery Sergeant Bass and the men of the third platoon are about to find out, and the answer carries a terrifying implication for the Marines-and the entire human race.