When the three younger Penderwick sisters go to Maine with Aunt Claire and are separated from oldest sister Rosalind for the first time in their lives, an uncertain Skye is left in charge as the OAP--oldest available Penderwick.

Greg, a self-confessed "indoor person," is living out his ultimate summer fantasy: no responsibilities and no rules. But Greg's mom has a different vision for an ideal summer one packed with outdoor activities and "family togetherness."