It's the first real day of summer: the day Belly, her brother Steven, and her mother Laurel head to Cousins beach to stay with Susannah Fisher, who's like Belly's second mother, and her boys, Conrad and Jeremiah. Belly's been going to Cousins since she before was born, but something about this summer feels different for Belly. And if the first night is any indication, she's right.

It's Belly's first day as a debutante, and a day of shopping and tea parties make her wonder if she made the right choice when she checked yes on Susannah's invitation. But when Cam shows up, things turn around for Belly. Her summer of firsts is just getting started. Meanwhile, Steven's having his own summer of romance, and Laurel is intrigued by a fellow author.

It's Belly's 16th birthday and her best friend, Taylor, arrives in Cousins to help celebrate. Belly's birthday is always her favorite day of the year, but this year she's blindsided by a secret Taylor has been keeping from her. The debs ask Belly who she's bringing to the debutante ball. Laurel and Susannah's secret finally comes to light.

It's the 4th of July, and the fathers have come to Cousins for Susannah's annual party at the beach house. Tensions flare between Conrad and his father. Belly and the Fisher brothers make margaritas, and chaos ensues. Later, Belly has a romantic moment that's interrupted.

Believing that Conrad might act on his feelings for her, Belly makes a decision. But when Belly and Conrad finally get a chance to talk, things don't go as she expected, and she wonders if she's had her eye on the wrong Fisher brother. Steven is assigned to work the poker room at the country club, and Laurel and Susannah have a night out.

Taylor comes back to town to play in the Cousins Beach charity volleyball tournament, and to help Belly, who's caught between Conrad and Jeremiah. When a yacht party with the debs ends in disaster, Belly's decision between the brothers becomes clear. Steven finds himself in over his head with Shayla's wealthy friends, and Cleveland helps Conrad through an emotional moment.

The debutante ball is here, but Belly's big night is almost ruined when Jeremiah learns the secret his mother has been keeping all summer. When Belly's left alone on the dance floor, someone else steps in to save the day. With Susannah and Laurel's secret out in the open, the season ends with a promise from Susannah and the confession from Conrad that Belly has been waiting for all summer.