Archie the cat, Sparky the mouse and Flo the bird have found a new home in a school, and can't resist helping out by using their special robot skills. They have to do it in secret, though, so none of the adults find out. When one of the children they have befriended accidentally causes a school computer to break, Archie promises to fix the problem. But then Archie starts to behave strangely. . . What's got into him? It's almost as if his programming has gone haywire! The Petbots realise he has downloaded a virus, and it's up to Flo, Sparky and their new human friends to work out a cure before Archie shuts down for good!