Plot Summary

Mild-mannered salesman David Mann (Dennis Weaver) is driving his red 1970 Plymouth Valiant through the California desert on a business trip.  After irritably passing a slow, dilapidated tanker truck spewing black smoke, the unseen driver retaliates by speeding past him and then slowing down again, initiating a deadly game of cat and mouse.

The truck driver, whose face is never shown, begins relentlessly stalking and terrorizing Mann. The harassment escalates from aggressive blocking and tailgating to attempted murder, including pushing Mann toward an oncoming car and crushing a phone booth Mann is using to call for help. Mann briefly stops at a diner, suspecting the driver is among the patrons, but a confrontation with the wrong man leaves him confused as the tanker waits outside.

As Mann’s car begins to fail mechanically, the chase intensifies through treacherous terrain. Realizing he cannot outrun the powerful truck, Mann decides to make a final stand. He jams his briefcase onto the accelerator, steers his car directly at the oncoming truck, and leaps to safety at the last second. The collision causes the truck to lose control and plummet over a cliff, exploding on the rocks below. The film ends with an exhausted Mann standing alone in the desert, tossing stones into the canyon as the sun sets.