While their elders are away at a wedding in Boston for the weekend, Alan and Nathaniel are trusted to stay on their own. Then Warren, inspired by an article in Life, comes up with an idea for a "dinner party" with Katie and her friends "the Marys," and Nathaniel is excluded. But the tables are turned on the boys when Nathaniel gets sick and the girls pay more attention to him than to them.

Nathaniel is upset when Jules and Sophie's cousin Myron, once partners in the hatmaking business, have a falling out at the weekly Friday night poker game and stop speaking to each other. In the meantime, Uncle Joel is helping George and Phyllis get through an income tax audit.

On a "once in a blue moon" Saturday, George is off work, so Alan and Nathaniel look forward to having some fun with their dad--but the adults decide "Family Chore Day" comes first. Well...that is until Grandpa, George, and the boys end up test driving a beautiful red Buick to Coney Island and Phyllis and Grandma play hookey at the new Danny Kaye movie with a stop for ice cream at Sid's afterward.