Continuity mistake: At end of the episode, when Sherlock leaves Detective Bell outside the 11th Precinct, Bell had a book and an envelope of which Bell puts the envelope in his pocket leaving the book, the next shot shows Bell turn and throw the envelope in the trash and the book disappears. (00:39:15)
Character mistake: Sherlock and Joan are looking at video footage of a restaurant called "La Porte Blanc", which is incorrect French. The right way is "La Porte Blanche."
Chosen answer: M broke into the brownstone and left a note. Holmes deduced he was staying at a high-class hotel from the soap scent on the note, and gave a picture from a hidden camera to his "irregulars" on the street to stake out hotels. One of them saw him, so Holmes followed him to his next intended victim and knocked him unconscious with a baton.
Sierra1 ★