A formulaic, far-fetched offering by disaster-thriller veteran Byrne (Mannequin, 1988, etc.). The centerpiece of Wildcat Mountain Amusement Park is the Thrill, a huge, old roller coaster. But when a girl is thrown from it and killed, the park's management is forced to close the ride and redesign it. Engineer Jack McKenzie, who's hired to review the design changes, is nearly killed by a runaway set of carscars, Jack discovers, that were sent out by someone who tampered with the Thrill's computer control system. This someone has plans to destroy the Thrillon the newly designed roller coaster's maiden run, with a full load of people. The logical suspect would seem to be the roller coaster's original designer, who publicly talks about revenge on those who want to alter his masterpiece, though he seems too old and feeble to be much of a real threat. From here the plot lumbers to an inevitable conclusion that includes murder, an in-the-nick rescue, and lots of flashy, if contrived, pyrotechnics (the saboteur is brought down with shoulder-fired fireworks). Engaging details about roller coasters, but uninspired thriller work.