Rim was a human colony world of the 2170's overrun by a Xenomorph outbreak
ten years before the Earth Infestation a family exploring the crash site of a downed alien spacecraft returned to the Rim colony with a medical emergency. The father who had discovered a clutch of alien eggs had been infected by a Facehugger the creature gestating inside him son hatched, quickly spreading the Xenomorph infestation though out the colony.
several weeks passed before a squad of Colonial Marines arrived at Rim to investigate, losing half there number to the Xenomorph threat in there first encounter. Marine Corporal Wilks and a ten year old girl named Billie were the only survivors. Evidence of the Xenomorph infestation was covered up and the deaths attributed to the explosion of the colony's reactor
- Billies experience on Rim mirror that of Newt's on LV-426 Newt's further adventures after Aliens were thrown out of continuity after her death in Alien 3 the planet Rim and the characters of Billie and wilks are retcoms of LV-428