On February 25th, 1885, George Longley, a train conductor, arrives in Montreal, carrying in his body the deadly smallpox virus. Doctor Thomas Rodger examines him, confirms that Longley has smallpox, and admits him to Montreal General Hospital. Later, he is moved to Hotel Dieu, a Roman Catholic hospital. Though Longley recovers and is released, Pelagie Robichaud, a worker in the hospital laundry, catches the virus on March 23rd, and dies on April 1st. Her sister, Marie, also contracts the virus and dies ten days later on April 11th. The smallpox virus is a hemorrhagic strain, called the “Black pox”, and is the worst kind possible. The outbreak has begun.

The city begins distributing vaccinations and the newspapers run articles warning the citizens of the outbreak, but in May, Dr. William Bessey orders that the public immunization program stop, due to side-effects in many of those who have received vaccinations. People can still get the vaccine from their personal doctors, but many doctors counsel against it. Doctor Alexander Milton Ross, a proponent of hydrotherapy (water cures) and a strong believer in clean living, is an especially loud critic of vaccination.