Owen has no friends due to his parents' profession of flipping houses, living in each for only a short period of time. His parents make a deal with him to allow him to get a dog if he is able to walk the neighbors' dogs daily with no mishaps for three months. After three months of incident-free dog walking, Owen's parents take him to the animal shelter to adopt one. Owen picks a dog caught that same day.
Immediately, Owen discovers his new dog, Hubble, to be extremely smart, knowing how to sit, stay, roll over, and play dead with no training. That night, Owen notices Hubble leave the house and follows him. He finds Hubble at the site of a crashed spaceship, with a bright beam of light connecting him to the sky. As Owen approaches Hubble, there is a bright flash, and Owen wakes up in bed the next morning.
Owen mumbles about what a weird dream he had, and is shocked to hear Hubble reply that it was more like a nightmare. Hubble explains that he came from the dog star Sirius and was attempting to contact them, when Owen got caught in the connection and accidentally gained the ability to understand dogs. note Hubble calls a meeting with the other neighborhood dogs, who are surprised that Owen can understand them.
Hubble explains that all dogs on Earth originated from the dog star Sirius 7, who were sent to Earth to colonize and dominate the planet. He tells the group that he was sent to Earth to assess the dogs' progress and return a report to the Great Dane, amidst rumors that not only had dogs failed to rule the planet, but some were actually being kept as pets. The dogs deny this outrageous and completely false rumor. They explain to Hubble that instead, they have trained their masters to feed them, groom them, bathe them, and pick up their waste. However, Hubble sees through this and realizes they are in fact pets.
Owen repairs Hubble's communicator and they receive a message from Sirius informing them the Great Dane herself is coming to Earth. Hubble tells Owen that with the state of things on Earth, she would surely give the order for global recall, recalling all dogs on Earth to Sirius 7. Owen and the dogs implore Hubble to help them prepare for the Great Dane's visit so that they will impress her. Hubble agrees, and Owen becomes friends with a neighborhood girl called Connie in the process.
Owen's parents finish renovating their house and are ready to sell it. During the open house, Hubble is kidnapped by two bullies who have been picking on Owen throughout the film. Hubble escapes and the dogs chase the bullies through the garage, being exposed to laughing gas in the process. The Great Dane arrives while they are impaired by laughing gas. When the Great Dane sees the chaos (and discovers that Owen can understand dogs), she gives the order for global recall.
All the dogs in the neighborhood disappear without a trace, leaving their owners puzzled. Owen's parents have no answers, and no one can accuse Owen of being involved since Hubble has disappeared as well. During the spaceflight back to Sirius 7, the Great Dane wonders why dogs have allowed themselves to become pets of humans on Earth. Hubble tells her that he believes the reason is friendship.
Just as Owen and his family is about to leave their house on moving day, Owen hears a sonic boom. His family and neighbors follow him to the landing site of the pod the neighborhood dogs have returned on. Hubble tells Owen that the Great Dane has categorized Earth dogs as a separate species, and allowed them to return on the condition that Owen's ability to understand dogs is removed. Seeing Owen's joy during the reunion, Owen's parents decide not to sell the house, allowing Owen to continue his friendship with Connie.
