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.
"Still training to be a sidekick, Katie protects the city against mysterious robot attacks--while trying not to feel like an outsider within her own friend group"--
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.