It Serves You Right to Suffer - S5-E9
Continuity mistake: When Joan accuses Agent Whitlock of gathering intel to Rip Off/ambush/rob the gangs, a woman enters the hall behind her. Moments later, The Woman disappears having never walked past Joan or Agent Whitlock. She didn't open any of the doors in the hallway either since she was walking straight down the hallway.
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 ★