Look out, Gull Island! Neeve, Phoebe, Kate and Hillary—the 12-year-old Callahan cousins—are staying at their grandmother Gee's rambling seaside estate. A whole summer without any parents! As the idyllic summer continues the girls discover that being joined at the hip isn't all it's cracked up to be. When the usually shy Kate launches a quest to become 'the cool' girl in town, her over-the-top antics threaten to pull the cousins apart.