Plot

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

Det. Murdoch is surprised to be called into a meeting with Chief Constable Giles and the mayor of Toronto. They've received a film from someone apparently gassing his dog. The city has also received a demand for $100,000 - or the entire city will be gassed. Using some of the evidence found in the film, Murdoch is able to locate the site where the extortionist killed the dog and the police find evidence of a very powerful poison having been used. They think they've solved the problem when they find and dismantle a gas bomb but Murdoch determines that the extortionist likely has sufficient gas to create many such bombs. They decide to evacuate the city - and only then does Murdoch realize they have it all wrong.—garykmcd

Mayor Clarkson is disappointed when Murdoch concurs with Chief Constable Giles's recommendation to take seriously a demand, by rhyming film, for $100,000 under threat to release in Toronto a lethal gas, which chemical expert Dr. Sanjay Prasad calls a terrifying novelty, as examination of the painstakingly identified demo site suggests it retains it toxicity in a huge, but sharply outlined area. He organizes a payment with officers undercover, but it's called not police-free, hence he demands a million, beyond the treasury means. Crabtree gets gas masks from the fire department but they won't do the trick, Brackenreid tells his wife to take their pre-teen sons on another Niagara holiday with her sister. A gas canister with release time mechanism is found and secured, combining with info found at the gas assembly spot after checking on mayor orders for deduced components suggests many more must remain threats. So station 4's own Cabbagetown quarter is to be evacuated, but discovering a personal link to an imminent execution changes everything last minute.—KGF Vissers