Cricket is disheartened by the prospect of another repetitive Green Family road trip. During a visit to Gwendolyn Zapp at BigTech to deliver produce, Cricket learns about Zapp’s plans for a space farm on an asteroid and a space hotel for the wealthy. Despite Bill’s initial refusal, Cricket strikes a deal with Zapp to farm on the asteroid in exchange for a free stay at the space hotel. He convinces the family to go, pretending it’s just a simulator. They soon realize it’s real when Bill nearly gets sucked into space, and they are joined by astronaut Colleen Voyd while Tilly befriends a glass-destroying creature named Cookie. Cricket and Gramma Alice, feeling restricted by Voyd, trap her in a cryo-pod.
The Greens face trouble on the asteroid when they are attacked by farm bots, leading Tilly and Alice to release Voyd. Voyd uses the escape pod to send produce back to Earth for Zapp, but the Greens learn that shutting off the robots requires reaching the energy compound on the asteroid. The compound’s destruction causes the silos to explode and the asteroid to lose its orbit. Cricket and Bill argue about their predicament, resulting in an explosion that sends everyone hurtling through space. Meanwhile, Nancy and Gloria, seeking answers, confront Zapp at BigTech and learn her true motive: proving her space farming dream to her kindergarten teacher, Mrs. Kay.
As the asteroid heads towards Big City, Zapp’s teacher congratulates her, but Zapp feels unfulfilled and plans to flee to Mars. Nancy and Gloria manage to contact the Greens and Voyd using Alice’s robotic leg. After reconciling, Cricket and Bill lead the group to the space hotel to use its tractor beam to bring the asteroid back. With Remy’s help, they get all the guests to safety using escape pods. Tilly gives Cookie to Voyd as they depart, and the hotel is destroyed while everyone escapes safely. The Greens decide to enjoy part of their vacation flying through space while waiting for a rescue pod.
During the credits, Gwendolyn Zapp is booed for abandoning Earth, leaving the Greens and Voyd behind. Voyd takes command of the BigTech space fleet, stepping into a new leadership role.