A married couple, Lynn and Doug Kaines (De Mornay and Silver), owners of an exotic furniture design company, visit Mexico, with Lynn in her first term of pregnancy. On their nighttime return trip, with her at the wheel, they accidentally run into and kill a Mexican police officer in the middle of the road. They make no report of the accident to avoid the perils of a Mexican jail, but slide the dead cop to the side of the road and return to the US. They have the front end damage to their car repaired clandestinely and appear to have gotten away with the killing.
Quite unexpectedly a vagabond named Jake Shell (Hauer), driving a dumpy old camper truck, shows up at their door hinting that he had witnessed the entire incident. Shell is a ne'er-do-well, parasitic, and pathetic excuse for a human being who blackmails the Kaines, who attempt to appease him. There is a physical confrontation with Shell and the Kaineses, along with perverse sexual innuendo, and a suspenseful attempt by the Kaines to rid themselves of their nemesis without revealing their secret.