There is disagreement whether Toronto should continue with Edison's DC system or Nikola Tesla's AC system, differences that seemingly result in murder.

When an anonymous madman threatens the citizens of Toronto with a deadly toxic gas, Murdoch must race against the clock to stop him.

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.

Detective Murdoch investigates the apparent murder of an inventor who is found sitting in a chair he invented. That chair was meant to provide a mild electrical current as a rejuvenation technique but Dr. Grace is certain that he was in fact electrocuted. He had a young woman with him the night he died but the investigation leads him to inventor Thomas Edison and the main suspect - his son Thomas Edison Jr. Meanwhile, the mayor tells Inspector Brackenreid to speak to Murdoch about Julia's plans to run in the upcoming election - fully expecting he will exercise his authority as her husband. Murdoch makes it clear to everyone that he has no intention of interfering and will support Julia in her campaign.

While investigating the murder of a rich benefactor and the theft of children's presents at a Christmas charity pageant, Murdoch discovers suggestions that a Christmas monster, a Krampus, may be involved.