What to read after The Adventure of the Red Circle?

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 who 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. The lodger insisted on having the Daily Gazette every morning, and sometimes requested other things. All requests were printed on a slip of paper left on a chair outside the room where meals were also left.