A young, disgruntled man with a background in explosives orchestrates a series of deadly accidents at amusement parks across the United States. His first attack kills several people on a rollercoaster, and the chaos draws the attention of government agencies and amusement park operators. As panic spreads, the authorities turn to safety inspector Harry Calder, an everyman with a knack for thorough investigation. He begins to piece together clues, realizing that the attacks are the work of a single elusive bomber who is targeting the parks for ransom.

Harry teams up with FBI agent Hoyt to track down the bomber. The extortionist demands a large sum of money and threatens further destruction if his demands are not met. Harry finds himself engaged in a tense cat-and-mouse game, trying to anticipate the bomber's next move while ensuring the safety of thousands of amusement park visitors. The situation grows more desperate as another threat looms, pushing Harry to use all his wits and resources to avert disaster.