Cameron prepares for his wedding at Ashford Mansion while struggling to fulfill a promise made long ago. His memories return to his childhood in Saratoga Springs, where he grows up in an abusive home and falls deeply in love with his best friend, Kara, who lives across the street.
Their lifelong friendship changes when Cameron leans in for a kiss and Kara pulls away. Heartbroken, he wanders into a cemetery during a thunderstorm and meets Eulalia, a mysterious girl sitting on the bench he and Kara once shared. Equally heartbroken after being abandoned by her boyfriend because she cannot bear children and is dying from a fatal brain illness, Eulalia becomes the person Cameron slowly opens up to. Through their meetings, Cameron relives his childhood with Kara, their attempt to remain friends despite his feelings, and his growing depression as his friends Tabetha and Rhode urge him to move on.
As Cameron's feelings for Kara continue to consume him, he repeatedly crosses paths with Eulalia, whose strange personality and connection to Ashford Mansion make her seem as though she doesn't belong in the same timeline. While Cameron struggles with rejection, failed relationships, and a toxic home life, Eulalia encourages him to find happiness despite the little time she has left. She eventually introduces him to her private world, revealing her dream of becoming a fashion designer before her illness took everything away, and recognizing Cameron's hidden talent for writing by gifting him a typewriter.
Meanwhile, Cameron's downward spiral continues. Drawn toward Curt, a carefree bisexual classmate, Cameron experiments with drugs in an attempt to escape his pain. Their friendship ultimately leads to Cameron being manipulated into a horrific sexual assault that leaves him abandoned by everyone he turns to for help. Broken and alone, he finds himself back in the cemetery, unknowingly completing the loop of how his story with Eulalia truly began.
As Cameron and Eulalia grow closer, she inspires him to write about his life, love, tragedy, trauma, and the feelings he has begun to develop for her. At the same time, Cameron's memories reveal a brief relationship with Kara that ultimately collapses, leaving permanent emotional scars. Strange events surrounding Eulalia continue to suggest that something beyond reality may be unfolding. Cameron eventually lets go of his desire to be with Kara, commits himself to becoming a writer, and submits his manuscript, *That Broken Branch We've Been Sitting on Too Long*, to a major competition.
When Cameron wins, he rushes to share the news with Eulalia, only to discover she is nearing the end of her life. Though he refuses to leave her, Eulalia insists he attend the award ceremony in Los Angeles, refusing to let herself become the reason he abandons his dreams.
After receiving the award, Cameron returns home to learn Eulalia has died. At her grave, he discovers she died on the very day he was born, leaving everything between them open to interpretation—either a twist in time or a trauma-induced illusion. A therapist later suggests Cameron may have imagined Eulalia after hearing the story *What Her Eyes Saw Before the Light*, written by Eulalia Varson Ashford before her death about a mysterious man who changed her life forever. Cameron embraces her legacy by changing his name from Cameron Clan to Cameron Varson.
Back on his wedding day, Cameron searches for ivory peonies, Eulalia's favorite flowers, and meets Nova, a young woman identical to Eulalia who shares his birthday and subtly hints at being her reincarnation. Cameron invites Nova to the wedding, which unfolds almost exactly as Eulalia once imagined. Afterwards, Nova experiences déjà vu around the mansion while Cameron quietly remembers Eulalia. He receives one final message from Kara asking to rekindle their friendship, but chooses not to respond, finally understanding there is **YOU** before **I LOVE YOU**.
In a post-credit scene, Cameron and Eulalia are seen together on a hill, planning a picnic.