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.