Mrs. Warren, a landlady, comes to 221B Baker Street with some questions about her lodger. A youngish, heavily bearded man, who spoke good but accented English, came to her and offered double her usual rent on the condition that he get the room on his own terms. He went out the first night that he was there, and came back after midnight when the rest of the household had gone to bed. Since then, neither Mrs. Warren, her husband, nor their servant girl has seen him.

After the landlady leaves, Holmes remarks to Dr. Watson that it seems likely that the person in Mrs. Warren's house is not the bearded man who made the arrangements. Holmes suspects that messages are being sent to the lodger.