In the vibrant yet treacherous world of Westerberg High School in Sherwood, Ohio, Veronica Sawyer (Winona Ryder) finds herself intertwined with a notorious clique known as the Heathers, comprising three wealthy and captivating girls who share her name: Heather Chandler (Kim Walker), the vindictive ringleader, Heather Duke (Shannen Doherty), and Heather McNamara (Lisanne Falk). The Heathers manipulate Veronica into participating in their cruel games, where they orchestrate pranks and spread vicious rumors to tarnish the reputations of their peers. In one particularly painful instance, Veronica is coerced into crafting a fake love note from jock Kurt Kelly (Lance Fenton) to the outcast Martha Dunnstock, leading to a humiliating encounter that devastates Martha.
As Veronica grows increasingly disillusioned with the Heathers' malicious antics, she yearns for the company of her true friends, feeling trapped in a situation that demands she betray her better nature. Her life takes a turn when she meets the enigmatic Jason "J.D." Dean (Christian Slater), a rebellious new student whose disdain for the Heathers mirrors her own. Their connection deepens when, in a heated confrontation, he brandishes a gun at the football bullies who harass him.
During a chaotic college party with Heather Chandler, where Veronica refuses a man's advances, Chandler's vindictiveness escalates, leading to a vow to ruin Veronica’s social standing. Distressed and embittered, Veronica vents her frustration in her diary, wishing harm upon the Heathers. When J.D. unexpectedly enters her life, their bond burgeons, rooted in a mutual desire to overthrow the clique's tyranny.
The plot thickens when J.D. proposes a sinister plan involving Heather Chandler. Although Veronica initially dismisses his intentions, an unfortunate mix-up leads to Chandler's demise, resulting in chaos that the school interprets as a tragic suicide, further elevating Chandler's status in death. As the Heathers’ domain crumbles, Heather Duke rises to power, donning a red scrunchy that signifies her ascendance.
Veronica becomes entangled in a web of manipulation when she and J.D. plot revenge against the boys who disgrace her. Their plans spiral further as J.D.'s increasingly reckless behavior alarms Veronica—especially when Martha, in a desperate bid for popularity, nearly takes her life. Upon realizing J.D.'s deadly intentions toward their classmates, including plans to stage a mass suicide, Veronica draws the line. She ends their relationship but remains mindful of her own safety.
In a climactic showdown, Veronica confronts J.D. just as he's set to unleash destruction at a school event. The tension culminates in a desperate struggle that results in J.D.'s self-sacrifice. Devastated yet resolute, Veronica emerges from the chaos to reclaim her autonomy, confronting Heather Duke and reclaiming her identity while inviting Martha to share a night of films, symbolizing her commitment to genuine friendship over hollow popularity. Through this tumultuous journey, Veronica transforms from a pawn in a cruel game to a powerful agent of her own fate.
