Belly sits at a friend's pool daydreaming of Cousins Beach, snapping back to the painful reality that Susannah is dead.

Belly discovers Conrad lying on a couch with his ex-girlfriend Aubrey in the basement on the day of Susannah's funeral.

Jeremiah calls Belly to say Conrad has abandoned his summer school program at Brown and gone missing.

Belly finds a blue jewelry box in Conrad's dorm room containing an infinity-symbol necklace she believes was meant for her.

Belly and Jeremiah arrive at the Cousins Beach house to find Conrad furious and refusing to return to school.

A realtor visits the Cousins Beach house to check on packing, revealing that Mr. Fisher plans to sell the property.

Conrad tells the realtor the house is not for sale, then privately asks Belly not to tell Jeremiah about his father's plans.

Mr. Fisher arrives and Conrad openly accuses his father of cheating on Susannah and abandoning her during her illness.

Jeremiah returns from driving off angry, carrying pizza and alcohol, and announces they are throwing a farewell party.

Belly puts on a home video, and the group watches their younger selves and a living Susannah on screen together.

Belly apologizes to Conrad on the beach for her behavior at the funeral, and he forgives her but walks back inside alone.

After getting drunk at the party, Belly calls her mother to confess where she is and beg for help saving the house.

Laurel arrives furious, and after Belly says Susannah will never forgive her for failing the boys, Laurel slaps her.

Laurel convinces Mr. Fisher at breakfast to give the beach house to his sons if Conrad returns and passes his exams.

Jeremiah pulls Belly into a kiss outside Brown, and Conrad arrives to witness it before confronting Belly about the necklace.

It's Not Summer Without You follows Belly Conklin, who is struggling after the death of Susannah Fisher, the beloved family friend whose beach house anchored every summer of her life. When Jeremiah calls to say Conrad has vanished from college, Belly joins the search and discovers—at the house itself—that Conrad is trying to prevent his father from selling Susannah's favorite place. The three young people are forced to confront their grief together, including an explosive family argument and an emotionally charged farewell party. Belly's drunk phone call to her mother brings Laurel to Cousins, where she fights for the house and brokers a deal that saves it. The summer ends with Jeremiah kissing Belly while Conrad watches, a confrontation over a necklace that symbolizes years of unspoken love, and Belly finally choosing to move forward.

The headline moments of a summer mission to save Conrad and the Cousins Beach house.

Taylor tells Belly she has been moping for months and pressures her to kiss Cory at a party to get over Conrad.

Belly comes home from a party to find the sandwich she left for her grieving mother still untouched on the counter.

On the night after Susannah dies, Jeremiah stops outside Conrad's door and hears his brother sobbing alone inside.

Belly and her brother Steven drive together to Cousins Beach for Susannah's funeral, neither knowing what to say.

After fleeing her confrontation with Conrad at the funeral, Belly locks herself in a guest room until her father checks on her.

Belly lies to her mother about going to Taylor's overnight and drives off with Jeremiah to search for Conrad.

Taylor secretly repacks Belly's overnight bag with her own clothing before Jeremiah arrives to take Belly on the trip.

Belly visits Susannah near the end of her illness and is shaken to see how much the disease has changed her.

Conrad and Belly share their first deep kisses by a fire at the deserted Cousins Beach house during a secret December visit.

Belly arrives home after her secret December night at Cousins and is grounded by her angry mother.

Belly drives into town for food and runs into a local shopkeeper who warmly asks after Susannah.

Belly opens a linen closet at the beach house, finds one of Susannah's hats, and is suddenly overwhelmed with grief.

After learning that Conrad and Belly kept the sale secret, Jeremiah argues with his brother and storms out in his car.

While waiting at Brown for Conrad's exams, Jeremiah tells Belly he was deeply hurt that she never reached out after Susannah died.

Conrad arranges a separate ride home the next morning, and Belly feels the rare satisfaction of being the one to leave first.

Beneath the main plot runs a current of smaller moments that reveal how deeply each character is struggling with Susannah's death. At home, Belly's isolation from her grieving mother and her impatient friends is shown in telling details—a sandwich no one eats, a light that stays on all night. The journey to find Conrad is colored by Jeremiah's long-buried feelings for Belly and by tender flashbacks to the December night she and Conrad first became intimate at the beach house. Back at Cousins, Susannah's presence is felt everywhere: in a floppy hat found in a closet, in a question from a local shopkeeper, in the grief no one knows how to voice aloud. By the end of the summer, Jeremiah has finally told Belly how much her silence hurt him, and Conrad chooses to disappear rather than fight for her.

The quieter scenes of grief, memory, and growing feelings beneath the surface of the summer.

Belly realizes she cannot evict Conrad from her heart without also losing her last connection to Susannah.

After catching Conrad with his ex-girlfriend at Susannah's funeral, Belly tells him she hates him and never wants to see him again.

Near the end of her illness, Susannah urges Belly to look after Conrad and tells her that he loves her.

Jeremiah recalls how his gut twisted with jealousy when Conrad showed sudden interest in Belly, and realizes he may love her.

Conrad secretly drives from college to Belly's house and takes her to the empty Cousins Beach house for an overnight visit.

Conrad stops their physical intimacy during the December visit and tells Belly he always wants to make sure she feels safe.

Belly realizes Conrad did not abandon school to run away but came to Cousins to prevent his father from selling the house.

Conrad sips Belly's slushy on the drive to Brown and references cocoa, revealing he still remembers their December night together.

Jeremiah recalls his father's lifelong favoritism toward Conrad and how a rare wrestling victory only felt real when Conrad acknowledged it.

During a pre-party game of Truth or Dare, Jeremiah dares Belly to kiss him the way they kissed as children.

After the party, Jeremiah asks Conrad privately whether he still has feelings for Belly, and Conrad claims he does not.

Belly calls Taylor from the party and hangs up after Taylor says Conrad may never have really liked her.

Belly watches Conrad studying and realizes she has been silently mourning the person he used to be, urging him to come back.

Belly unclasps the infinity necklace and hands it back to Conrad, internally vowing never to run back to someone who pushes her away.

Belly runs toward a car in a white dress in the pouring rain, knowing her uncertain future still belongs to her.

Running beneath the surface of the summer are the pivotal moments of discovery and decision that shape Belly's emotional growth. From Susannah's final request that Belly look after Conrad, to Jeremiah's jealous realization that he loves her, to Conrad's secret drive to give Belly one perfect winter night, the story is built on unspoken feelings and deferred truths. Each revelation chips away at Belly's certainty about Conrad—his refusal to say what the necklace means, a slushy sip that proves he still remembers their December night, and Jeremiah's long-suppressed kiss that shocks her back to the present. Belly must reckon with a version of love that is all promise and no action and decide whether that is enough for her anymore. By the time she runs toward a car in a white dress in the epilogue, the answer is clear: her future is uncertain, but it is finally, fully hers.

The private turning points and revelations that push Belly toward choosing herself over nostalgia.