Murphy the cat, Bubbles the dog and Captain Cockle the parrot live in a pet shop. When the owner's niece Keira comes to stay, she is entranced by the animals but a bit puzzled, because her Aunt Emily never seems to actually sell any of them. But then one day a strange woman arrives at the shop. She is Henrietta Fysshe-Pye. She has just bought the castle on the edge of the town and now she wants some animals to populate it. She chooses Mulvey, Bubbles and Captain Cockle and is determined to have them despite Keira and her aunt's attempts to persuade her otherwise. The other animals in the shop are horrified - Murphy is their leader and has been living in the shop since he was a kitten, so once he and the other two have been taken by Mrs Fysshe-Pye, the animals left behind decide they must rescue them.