In the small mining town of Valentine Bluffs, preparations are underway for a Valentine's Day dance, the first in twenty years since the town was scarred by a tragedy. Two decades prior, a mining accident occurred when supervisors left their posts to attend the town's Valentine's Day dance, resulting in an explosion that trapped miners below. Only Harry Warden was found alive, driven mad by the ordeal, who later committed murders and was institutionalized. He vowed further bloodshed should the town ever hold another Valentine's Day celebration. Despite warnings, the townspeople are eager to dismiss the old legend and revive the dance.

As the dance draws near, a series of brutal murders begins to plague the town, with the victims found in a manner reminiscent of the legend of Harry Warden. A heart in a box with a threatening note warns the townsfolk to cancel the dance or face further consequences. As fear escalates, suspicions arise that Warden may have returned to enact his revenge. The local sheriff and mayor face the difficult decision of whether to proceed with the festivities and risk more deaths, or to heed the warnings and stop the celebration in hopes of stopping the bloodshed. The town is caught between preserving tradition and protecting its citizens as an unknown assailant casts a shadow of terror over Valentine's Day.