Kalifornia (1993)

Brian Kessler, a journalist researching serial killers, and his photographer girlfriend Carrie set out on a cross-country tour of the sites of the killings. Sharing the ride and their expenses are Early Grayce, a paroled white trash criminal, and his girlfriend Adele. As the trip progresses, Early begins to appear more and more unstable, and Brian and Carrie begin to fear that they may have a real-life killer in the back seat of their car.