Diane Weston, a university professor, has a careless fling with Jeff Dante, one of her students. Realising her mistake, Diane tells Jeff that it's over, but he refuses to let her go. Even more unsettling is that Jeff was a prime suspect when his previous lover, also a professor, died mysteriously after cooling their romance. Jeff is on the edge of insanity and he begins stalking Diane. Soon after, Diane's daughter Tess invites her new boyfriend home to meet her parents. Diane is panic-stricken when Tess' new friend turns out to be Jeff. It soon becomes frighteningly obvious to Diane that Jeff will do anything to get what he wants, no matter who has to pay the price.