The death of a five-year-old boy from a respiratory illness energizes the entire city of Riverside, Connecticut. The source of the illness is a mystery. The physician who treated the boy thinks that the polluted air over Riverside might be the root cause. A pro-active city employee, Rose Nardello, agrees with the physician and convinces the Riverside city manager to initiate corrective action. She recommends the city retain an emissions expert. The chief executive officer of a diesel engine manufacturer recognizes that an emissions investigation could threaten his firm's very existence. He hires a hit man-a disgruntled former F.B.I. agent-to eliminate the emissions expert. When Rose discovers that her father helped the chief executive officer find the hit man, she is involuntarily propelled into the middle of a murder investigation.