Ten years after a covert military experiment on a remote Pacific island went wrong and killed eighteen servicemen and his assistant, Dr. Richard Long (DAVID PAYMER) is still trying to forget the havoc and death his experiment wrought. Living in the small town of Jerome, Montana, Long still conducts scientific experiments at the local base, but far more enjoys his time fly-fishing with Tim Mason (SKEET ULRICH), a loner/drifter who works in the local greasy spoon and has a checkered past.
Long's life changes, and then ends, when he's visited by Andrew Brynner (PETER FIRTH), a former military officer who took the blame and served ten years in Leavenworth for Long's lethal experiment. Now a free man with a score to settle with his country, Brynner has assembled a team of high-tech terrorists, including icy blond Vaughn (HUDSON LEICK), and plans to steal and then sell "Elvis" -- Long's highly volatile, blue crystal substance -- to the highest international bidder.
Unfortunately for him, Long has already delivered "Elvis" to Mason, along with the directions that the substance remain below fifty degrees Fahrenheit lest it detonate and kill everyone within several hundred miles of it. After Mason and Arlo (CUBA GOODING, JR.), a wisecracking ice cream delivery man, have a run-in with Brynner, they set off en route for Fort Magruder, some ninety miles away.
The two men don't get along with each other -- Arlo only agrees to transport the temperature dependent device in his ice cream truck because Mason held a gun on him -- but find a common bond in trying to avoid Brynner and his team. With the help of Colonel Leo Vitelli (DANIEL HUGH KELLY), who shows up late in the game to assist, Arlo and Mason do what they can to survive Brynner's attacks, avoid the local deputy, Pappas (JIM GRIMSHAW), who's also hot on their trail, and keep "Elvis" below fifty degrees.