Puggy is back for Part Two in the Spy Dog series. Previously in "A Suspicious Neighbor," Puggy saw a news report discussing the disappearances of dogs around the city. Right around that time, Puggy noticed that his next-door neighbor did not look like a typical human. He learns later that the man is an alien who is responsible for the disappearances of the animals. The alien was experimenting with the dogs so that they could be modified with advanced technology. Due to a twist of fate, Puggy finds himself modified and it was up to him to stop the alien while making sure his owner Bill doesn't find him out."Cat's Revenge" begins when Bill comes home one day more excited than what he normally is. The reason for this is because Bill won a cat in a raffle! Unnerved by this, Puggy couldn't do anything but become jealous of the fact that the cat would probably earn more of Bill's attention. When the cat finally does arrive, Puggy is alarmed to see that the cat was the same cat from the alien's house that he had beaten months before. The aliens were back and they were using the cat, who they call Killer, to complete their goals. Puggy is now on the journey to fend off Killer and stop the aliens from acquiring his body, his home, Bill and the entire world. However, Puggy is not alone in this battle because Mannie, his Jack Russell friend, is here to aid him. Will the dogs succeed in taking down Killer and the aliens, or will Killer be too much for Puggy to handle?