Intensity

Intensity is a 1995 horror novel by the American writer Dean Koontz. Koontz set out to subvert the common belief that thrillers need slow stretches between moments of excitement. Instead, he keeps the tension high from beginning to end, moving from one conflict to the next with almost no release.

The protagonist is Chyna Shepherd, a twenty-six-year-old woman scarred by a childhood of neglect and abuse, who lives in a state of constant wariness. During a long weekend at the country house of her best friend, Laura Templeton, she finds for the first time a sense of acceptance she had never known. That calm is shattered when Edgler Vess, a serial killer, breaks in and methodically kills the household. Chyna survives and, following the killer's trail, discovers that he is holding a teenage girl, Ariel DeLane, who has withdrawn into catatonia.

Vess sees himself as a "homicidal adventurer" who seeks intensity in every experience, and he is one of the genre's most unsettling villains. The chapters alternate between the perspectives of the two characters, which sharpens the sense of a race against time. The novel has been compared with the French film High Tension (2003). Its director acknowledged having read the book, though Koontz chose not to take legal action.