Jim has recently acquired a new pet, a "roundhead" called Willis (voiced by Pat Fraley) 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.
are about to be sent off to a boarding school, their mother (voiced by Marcia Mitzman Gaven), the colony's medical officer, discovers a substance deep within the mines that is killing the miners.
In the end, only Jim and Willis' friendship save the colony world from destruction by the angered natives, who reveal themselves to be an intelligent, highly advanced subterranean race.
Willis, now a full-grown Local, has befriended Jim's young granddaughter, and spends time with her wandering the grass-covered hills and telling her stories of the adventures he and her grandfather had together.