Everbody knows that cats chase mice. And what's more, they catch them and eat them too. At least normal cats do...but Martin is no ordinary kitten. To everyone's embarrassment he prefers tinned cat food to real mouse. When at last he does catch a mouse, he decides not to eat it, but to keep it as a pet! Martin and Drusilla the mouse get on splendidly, until the terrible day when Drusilla disappears and Martin is sold to a large lady who lives in a fourth-floor flat.