After Carrie’s boyfriend Sebastian and best friend Maggie betrayed her last season, Carrie is determined to make the most of her summer, living with Walt in Manhattan – and all the grit and glamour it has to offer – even agreeing to a night on the town with Donna LaDonna. But when Donna shows up with Sebastian, Carrie decides to go out on her own, and by a series of surprising events meets one of the greatest loves of her life, Samantha Jones. Back in Castlebury, Mouse shuts out Maggie when she sees her working at the country club, and Dorrit has her own problems to contend with when Tom finds out about her boyfriend Miller.

Carrie and Walt are faced with kicking out their new roommate when she makes herself too comfortable. Walt summons the courage to tell Bennet how he feels about him at his eighteenth birthday bash – at a VIP Z100 concert – but things go horribly awry before Bennet can respond. Samantha and Mouse meet, and Samantha wastes no time giving Mouse sex tips. Back in Castlebury, Sebastian and Maggie run into each other; and the evening doesn’t go exactly as planned when Tom invites girlfriend Deb to spend the weekend with him.

Larissa returns from her summer in Kyoto and insists on taking Carrie and Walt to a fabulous Japanese festival in the city, where Larissa meets Samantha, with an explosive result. Samantha seduces an acrobatic Ninja. Back in Castlebury, Carrie’s plans to remain Zen backfire when she finds herself locked in a classroom alone with Sebastian. Mouse helps Maggie with her college applications, but Maggie is distracted when somebody from her past reappears. Meanwhile, Walt worries that his classmates will sense he is gay, and Harlan makes an offer Tom can’t refuse.

Carrie pitches Larissa a profile on New York wunderkind playwright Adam Weaver, but when he proves a difficult, yet fascinating, interview, Carrie’s job is on the line. Bennet’s rules in his relationship with Walt force Walt to acknowledge his real feelings. Carrie and Dorrit are surprised to find a common enemy in Tom’s girlfriend Deb’s son Dylan. Meanwhile, Sebastian seeks comfort in the arms of someone new.

When Sebastian learns that his mother is getting remarried, he asks for Carrie's dad to make sure she is legally protected. Carrie is furious when she discovers that Weaver has secretly read her journal. Mouse volunteers to help with the Homecoming float, but tries to distance herself when West wins Homecoming King. Samantha finds herself a place to live and another unusual job. Meanwhile, Dorrit begins to feel smothered by Miller, especially when he befriends her dad, and Donna LaDonna gives Dorrit some wise advice.

When Carrie struggles with writer’s block, Weaver tries to help but gets in the way. Maggie and Sebastian grow closer after learning some shocking news. When Bennet moves to a dangerous neighborhood, Walt takes drastic measures to keep himself safe, with both hilarious and heartfelt results. Meanwhile, Larissa and Samantha finally find some common ground: sex.

Carrie is shocked when she reads a nasty rumor about her in a New York City gossip rag, but Samantha has a plan to set the record straight. Walt steps in when Bennet feels taken advantage of at Interview. Mouse, worried that she and boyfriend West are stuck in a rut, does something very risqué. Meanwhile, when Maggie experiences a medical emergency, Sebastian is forced to reach out to the one person who can help.

Larissa gives Carrie some harsh advice about her relationship with Sebastian. When Harlan asks Tom to work overnight on a top-secret case, Dorrit decides to throw an impromptu get-together, which quickly spirals out of control. Meanwhile, Mouse and Donna get surprisingly close and Sebastian makes a hasty decision after another fight with his parents.

Walt and Bennet get some devastating news that forever changes their future. Sebastian gets an exciting work opportunity, causing him to bail on Carrie on Valentine’s Day, much to her chagrin. When Maggie accidentally enlists in the army, a surprising duo comes to her rescue. Elsewhere, Tom uses some reverse psychology to encourage Dorrit to start dating again.

When Bennet starts slacking at work, Carrie tries to cover for him. However, when Larissa finds out, things backfire big time for them both. Samantha makes an uncharacteristic decision about her latest fling. Sebastian’s father asks him for a favor that could change Sebastian’s future forever. Meanwhile, Tom is hoodwinked by another – beautiful – lawyer when negotiating a deal, and is advised by the person he least expects.

Carrie, Mouse, Maggie, and Walt decide to go to their senior prom – at The Waldorf Astoria – together for a final hurrah. Larissa offers Carrie an opportunity that makes her rethink her plans for the next year. Mouse learns a secret about Donna LaDonna that could threaten her reign as queen bee. Meanwhile, Sebastian hides a big decision from Carrie.

Things grow increasingly tense between Carrie and Tom. When Larissa drops an unexpected bomb on Carrie, Sebastian decides he, too, needs to come clean about something. Maggie turns to Walt when she thinks Pete is cheating on her, but gets the surprise of her life. Mouse and West find themselves in a sticky situation. Elsewhere, Samantha considers leaving the city, and Larissa's wedding to Harlan is out of this world.