Rex arrives home to find that there's a mouse in the kitchen. But this is no ordinary mouse, he is preternaturally strong, extremely aggressive and refuses to be kicked out. The Gang even resort to getting Tiddles the Cat round to sort him out. Then the mouse reveals that he was once Rex's pet mouse, Morris, who Rex sold to Dr Dogg for animal experimentation. A tearful reunion ensues.

Bob's eating is growing out of control. Rex suggests that Bob needs to watch what he eats and exercise, but Bob has a better plan: plastic surgery courtesy of Dr Dog.

The Gang discover a prototype hover mower whilst clearing out Bob's shed. The major design fault is obvious when it burrows into the ground, creating a tunnel that leads all the way from the back garden to Australia. A shouting match with some dingos follows, at the end of which an enraged Bob accidentally throws Vince down the hole, precipitating an adventure of global proportions.