Meet the Melendy children: Mona, Rush, Miranda (Randy), and Oliver, who are tired of boring Saturdays in 1940s New York City. They form the Independent Saturday Afternoon Adventure Club (I.S.A.A.C.), pooling their allowances so each child can have one magnificent, solo adventure per month. Through these outings—from the opera to the circus—each sibling discovers new passions, faces unexpected challenges, and learns about independence and responsibility. Their adventures strengthen their bond as a family and open their eyes to the fascinating world beyond their brownstone home.