As spring arrives on Gardam Street, there are surprises in store for each Penderwick, from neighbor Nick Geiger's expected return from the war to Batty's new dog-walking business, but her plans to use her profits to surprise her family on her eleventh birthday go astray.

The Penderwick family return to Arundel for Rosalind's wedding, but Lydia, who has only heard stories of the grand estate, is eager to explore the place where her older siblings had endless adventures.

When a reporter plans an exposé that could shut down the School of Fear, Garrison, Lulu, Madeleine, and Theo seek help from Bishop Basmati, head of the nearby Contrary Academy, whose hyperactive, fearless, and extremely impulsive students soon overrun the School of Fear.