The film starts back in 1988, during a Valentine's Day dance at Robert Kennedy Middle School in San Francisco. A young and awkward Jeremy Melton, portrayed by Joel Palmer, musters up the courage to ask four girls to dance: Shelley Fisher, Lily Voight, Paige Prescott, and Kate Davies. Unfortunately, each one of them harshly declines his invitation—Shelley mockingly exclaims, "In your dreams, loser!", while Lily simply responds, "Eww!" and Paige adds, "I'd rather be boiled alive". Only Kate, showing a hint of kindness, tells him, "Maybe later, Jeremy." Dejected, Jeremy turns to another girl, the heavier set Dorothy Wheeler, who invites him under the bleachers. They share a moment of intimacy that is abruptly shattered when a group of bullies, led by Joe Tulga, shows up. Dorothy suddenly accuses Jeremy of being a "pervert," igniting the bullies’ rage. They ruthlessly strip Jeremy to his underwear and beat him as the crowd of students watches with laughter, leaving Jeremy to seethe with anger.
Fast forward to present-day Los Angeles, where Shelley (Katherine Heigl), now a medical student at UCLA, finds herself on a disheartening date with the self-absorbed Jason Marquette. Regretting her decision, she excuses herself to study for an exam at the morgue. While there, she discovers a Valentine addressed to her, ominously signed "J.M." The note chillingly states, "The journey of love is an arduous trek. My love grows for you as you bleed from your neck.". Shelley’s night takes a nightmarish turn when she is ambushed by an attacker clad in a black coat and a Cupid mask. Trapped and desperate, she hides amongst cadavers but is ultimately found, leading to her brutal murder.
The narrative shifts to San Francisco, where Kate (Marley Shelton) and Paige (Denise Richards) are preparing for a turbo-dating session. As they discuss Kate's troubled boyfriend Adam (David Boreanaz), the news of Shelley's murder interrupts them. The story progresses through their attempts to cope with the escalating horror, leading to the girls attending Shelley's funeral. Among the attendees are Lily and Dorothy, who are summoned by Detective Vaughn for inquiries. The plot thickens when Dorothy receives a Valentine with a similar sickening message signed J.M., igniting fears among the group.
In an interconnected web of jealousy, suspicion, and betrayal, each character finds themselves drawn deeper into a sinister game of danger. The Cupid killer strikes at a photo exhibit, where passion turns deadly, leading to Lily's shocking demise. The group grapples with increasing terror as it becomes clearer that Jeremy Melton’s revenge is far from over. Meanwhile, the treachery unfolds at Dorothy's Valentine's Day party, destined to become the stage for impending doom.
As the killings escalate, the friends must confront their dark past and the mistakes they made in their youth. Tensions rise, especially between Kate and Dorothy, revealing a toxic cocktail of resentment that has simmered for years. With everybody under threat and the killer lurking, "Too bad, so sad" taunts echo through the air. Closer relationships disintegrate as each twist of fate leads towards a climax filled with shocking revelations about identity and revenge.
Through chilling sequences, the truth about the relationships among the characters disintegrates. Ultimately, as layers unravel, it is revealed that Adam is not who he seems, and the vengeful figure behind the mask is none other than Jeremy Melton—seeking the ultimate retribution. The chilling final moments leave the audience grappling with the horrors of their past and the consequences of their actions. As the camera pans, a drip of blood reveals the horrifying twist that changes everything: the real mastermind behind the terror was disguised all along.
