Allen is left behind on Earth after stowing away on an alien spacecraft. When Robbie helps Allen out of a jam, he follows her home, and meets her brother.

Robbie and Josh devise a plan for enrolling Allen in their school. Complications arise when Allen's `dad' is expected to come along too.

In an effort to protect Allen, Robbie follows him and Latanya on their hike through an abandoned mine, and starts a dangerous avalanche.

A creature called a Gronpoly lands on Earth and wreaks havoc at the Stevenson house and at Robbie's new job. Government agent Shaw tracks the Gronpoly and Allen.

Allen's just found out about Christmas. Now he'll give Robbie the best present ever. But Josh's mistake could ruin it for everyone.

Allen experiences an earth disease for the first time and the common cold nearly costs him his life.