Murdoch says the letter could not have come from NY as it had an Ontario stamp. Stamps in the time of George V were from Canada Post, not stamps from each province.
George and Effie find a mouse that had died from carbon monoxide poisoning some time after they had entered the Sunrise Suite, according to Effie, who said it wasn't there before. Carbon monoxide rises to the ceiling. If there was so much carbon monoxide in the room that it could've gotten down to the mouse's level to kill it, George and Effie would have felt the effects (and died) long before the mouse died.
The city of Thunder Bay did not exist until 1970 when Port Arthur and Fort William were amalgamated so the gentleman had to be from either or.
Near the beginning, George and Effie talk about being in Hampshire (England). A steam train is seen, implying this was how they got there. Unfortunately, the train shown was travelling along the Glenfinnan Viaduct which is in Scotland, over 540 miles away.
A character is mentioned as coming to Toronto from Thunder Bay. In early Toronto times, Thunder Bay didn't exist- there were 2 separate cities- Fort William and Port Arthur. An anachronism for certain.