Zenon Kar, Kirsten Storms is 15 years old and still not wise to the dangers of meddling. When she shows Nebula Wade, Shadia Simmons a new game and how to play it, she accidentally empties Commander Plank's office and is assigned work detail in the Alien Patrol lab. It is also revealed that Greg broke up with her. The space station is now under military command, and General Hammond, John Getz, is assigned to lead. He decides Zenon should look after his daughter, Margie Hammond, Lauren Maltby, a headstrong girl who sees Zenon as a rival and threatens to have Zenon and her family kicked off the space station if Zenon doesn’t obey her.
Zenon finds herself in a caretaker role, and Margie’s constant pressure fuels a tense, playful rivalry between the two girls. Margie’s demanding nature pushes Zenon to prove herself, even as Aunt Judy Kling, Holly Fulger, tries to keep the peace with humor and warmth. The clash between mentor and foster-sibling becomes a driving force in the day-to-day life aboard the station, while the looming question of authority hangs over every prank and plan.
When a signal reaches Earth from aliens who seem eager to meet Proto Zoa, Zenon and Margie hatch a plan to track down the reclusive star. With Aunt Judy alongside them, Nebula Wade, Orion the Alien Patrol lab guy, Proto Zoa, and Zenon’s mother Astrid Kar, Susan Brady, in their party, the girls set off on a bold quest. Proto Zoa, Phillip Rhys, who feels his peak career has passed, is coaxed into joining the group. The mission to locate the aliens leads them to a moonbound rendezvous, a leap that tests their courage and camaraderie.
The trip to the Moon is perilous: their ship runs out of fuel and nearly crashes, but the aliens arrive to pull them from the brink. On the Moon, Zenon meets the aliens face-to-face and discovers they are friendly. Through telepathic communication, the aliens reveal they have been lost in space for three years and need the ship’s navigation charts to return home, politely asking for the information rather than taking it by force.
After securing the charts, the group returns to the space station only to face a stern reality: the station is in fragile condition due to sabotage, and General Hammond remains resolved that it is too dangerous to stay in orbit. Margie finds her voice and pushes back, and the aliens make a dramatic return to lend their assistance. They push the space station back into a stable orbit and restore the previously decommissioned sections as a gesture of gratitude for the help they received.
With the crisis averted, Commander Plank and General Hammond come to a working arrangement and agree to share command. Plank and Aunt Judy marry in a ceremony that Proto Zoa performs, dedicating a new song to Zenon as a sign of renewed inspiration for the young hero. It becomes clear that the aliens had been attempting to reach Zenon all along, not Proto Zoa, using the transmission of his old concert to make contact. Margie decides to stay, and she and Zenon form a genuine friendship. Zenon also finds a potential love interest in Orion, the scientist who helped shepherd their mission, closing one chapter and opening another for their shared adventures among the stars.
