Detective Murdoch and his colleagues face an entirely new dilemma when they find a local industrialist, Richard Welch, tied down at the top of a telephone pole with a noise-activated bomb strapped to his chest. Mayor Clarkson orders all industries in the area shut down and the police do their best to keep the noise pollution to a minimum. Under pressure, the mayor eventually relents and work resumes, but not until after the bomb is detonated by a loud car horn. The next victim turns out to be the mayor himself and Murdoch has only 3 hours to find the culprit and deactivate the device. Meanwhile, Julia is increasingly frustrated as Murdoch has yet to ask her the big question.

La investigación de Murdoch sobre el asesinato de un policía es obstaculizada por la interferencia del reemplazo excesivamente entusiasta de Brackenreid.