Mervyn is a self-centred cat so when his family go on holidays without him he is indignant. Worse still, they leave him in the care of Elsie Lavender, the next-door neighbour, who has a little terrier dog called Amos. Mervyn sets out to take his revenge by playing pranks on Elsie and Amos. The family, however, play a trick on Mervyn when he sulks upon their return.