Continuity mistake: At the beginning, the way Holmes holds the photo is different in consecutive shots. (00:01:00)
Character mistake: The number of victims of the balloon man changes from seven to eight between the initial scene where he is introduced and where Holmes finds out the identity of the original balloon man.
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 ★