Jim Marlowe, Jr., and his little sister, Phillis Jane “P.J.” Marlowe, are teens growing up on the distant mining world of New Aries. Life on New Aries is difficult, with its surface being a red-colored desert. Along with the harsh climate and severe weather, there are many dangerous creatures living on New Aries, such as the three-headed Cerebus Hounds, the swift and voracious Water Seekers, and the misunderstood Locals, creatures so rare and dangerous they border on urban legend. Jim has recently acquired a new pet, a “roundhead” called Willis with the parrot-like ability to mimic human speech and record conversations. Willis is small, furry, and playful, can survive both on the surface of New Aries and the Earth-like atmosphere of the colony, and has some sort of connection with the Locals on an almost empathic level. As Jim and P.J. are about to be sent off to a boarding school, their mother, the colony’s medical officer, discovers a substance deep within the mines that is killing the miners.