Testing a new Flipspace protocol, the Mockingbird travels to its most distant mission yet. There, Colonel Rama orders Major Fitch to lead a surface team to a planet outside the habitable zone, yet teeming with life based on ammonia. Rama flies a second science team in studying the remaining planets, where an artificial satellite is found. Fitch’s team also finds traces of civilization and discovers a lingering threat that destroys technology. The study of fallen societies turns into defense from a planet-wide force.