Guinea PIG, Pet Shop Private Eye Book 2: And Then There Were Gnomes

Sasspants, reluctant Guinea Pig PI, solves the case of the pet ship ghost (and the multitude of missing mice) with the help of her sidekick, Hamisher the Hamster. Once again, they must circumvent well-meaning pet shop owner Mr. Venezi, who still cant tell mice from walruses or hamsters (in birthday hats) from gnomes.