In the third and final book in the middle grade trilogy that Newbery Honor winner Rita Williams-Garcia raved is brimming with hilarity and sisterly hijinks, Marigold, Zinnia, and Lily Silver return to Cape Cod for another unforgettable summer. This summer, the town of Pruet is turning 300, and a huge celebration is planned. On their first night back east, the girls make a promise not to fight with each other, ensuring that this will be the best summer yet. It shouldn't be too hard. Each sister, after all, has her own focus during the visit. Marigold makes it her mission to befriend Chloe, the famous director Philip Rathbone's niece, who is working on the set of her uncle's upcoming television series. Zinnie is busy creating an attention-grabbing blog to help her chances of becoming editor-in-chief of her school's literary journal. And Lily has become quite the explorer with her science day camp group. All seems to be going smoothly until Zinnie's growing friendship with Chloe leaves Marigold feeling hurt. Her little sister is stealing her new best friend-why can't Zinnie just stop intruding on Marigold's life? With the divide between the girls growing deeper, Marigold, Zinnie, and Lily worry it's impossible for them to go a summer without a big fight. The same silver moon may hang in the night sky each year, but the sisters below it are changing in ways they have yet to understand. If they grow apart, more than a promise could be at risk. But if they grow together...the sky's the limit.