Goofs

A group of children is depicted trick-or-treating at Flaherty's Tavern for Halloween. The practice of trick-or-treating - or, as it originally was known, "guising" - was not introduced in America until the 1910s, and the phrase "trick or treat" did not appear until the 1920s.

At the end in the bedroom, Dupin is thinking out loud in trying to solve the mystery of where Thevenet's missing will is. Dupin mentions that the barometer on the wall, toward which Thevenet's eyes were gesturing before he died, offered a hint to locating the will. Suddenly, Dupin notes that the cold temperature in the room was indicative of a barometer reading that is falling. However, this is an erroneous association, as barometers measure atmospheric pressure, a reading that has nothing to do with temperature.