Twelve-year-old Katie is dreading the boring summer ahead until she realizes the mysterious neighbor who hired her to catsit is one of the city's greatest supervillains.
In every season a little mouse pops out of his hole in the meadow and explores his world, gathering the food and supplies he will need when winter comes.
Guinea pig Sasspants knows something is wrong with ninth-grader Viola, the new pet shop assistant, so when Mr. Venezi goes missing Sasspants and Hamisher put their private investigation skills to the test.
Sasspants, the reluctant guinea pig private investigator, is drawn into another mystery by Hamisher the hamster who believes there is a ghost in the pet shop.
When guinea pig Sasspants leaves Mr. Venezi's pet shop to live with Detective Nichols, and hamster-detective Hamisher retires, the case of the missing bookstore cat must be solved without their help.