Owen is a boy who walks people's dogs. He really wants a dog for himself. So one day he goes to the dog shelter and adopts Hubble. Owen soon finds out that Hubble is a very starnge dog and very clever. One night Owen follows Hubble up a hill and the next morning Owen finds himself talking to dogs. Owen soon learns that Hubble is from Sirius, the dog planet and that he has come on a mission to see what Earth dogs are like. He's not very impressed, but Hubble has another problem. The Greater Dane, who is the ruler of Sirius is coming to Earth and if she's not impressed, then she'll take every dog on Earth back to Sirius!