As he walked down the neglected avenue he heard the harsh, cracked voice of Mad Martin piping a tuneless ditty, and shortly afterwards met with the man himself face to face. With his lean, bent form, picturesque rags, and venerable white beard, the man looked like Lear, insane and wretched. When he saw Gebb, the creature stopped singing, and broke into a cackling laugh, which had little mirth in it Gebb--usually self-controlled and careless of impressions--shuddered at that merriment of hell. "Are you in love with her too?" he asked the detective. "No," replied Gebb, humouring the man. "Why do you think so?" "John Alder came here and loved her," said Martin, reflectively. "Arthur Ferris came and loved her. I thought you might be a third. But you won't win her heart--oh no! Young Arthur has done that. Tall, straight, dark, handsome Arthur, with the mark of Satan on his cheek." "The mark of Satan!" repeated Gebb, puzzled by this description of Ferris. "Hist!" cried Martin, with uplifted finger. "He is a wizard and she a witch, and they dance in the Yellow Room when the moon is up. Young Arthur has a red mark on his cheek; Satan baptized him there with blood. Oh, blood! oh, blood!" moaned the wretched creature, "nothing but blood. "'A knife for you, and a rope for me, And death in the Yellow Room; I am alive, and you are dead, But each hath gotten a tomb.'" And with a long, dolorous cry Martin ran up the avenue swinging his arms, leaving Gebb to puzzle out his enigmatic verse as best he could. CHAPTER XII THE DIAMOND NECKLACE Gebb, much to his disgust, returned to Norminster as wise as he had left it. Beyond meeting a lunatic, and interviewing an obstinate young woman, he had spent his time and money to little purpose; and it was with a perplexed brain that he sat down to consider his future movements. In the face of his failure he was at a loss how to act. Miss Wedderburn, with what looked like deliberate intention, only repeated the story he already knew. Miss Gilmar had confessed to a fear of Dean. She had fled from the Hall on account of that fear; her travels and hidings and extraordinary precautions had been undertaken solely to thwart the revenge of Dean. Gebb was aware of these facts; but there was nothing more in them likely to instruct him. He had, so far, exhausted their capabilities. "What am I to do?" he asked himself for, say, the fiftieth time. "How am I to act? In which direction am I to move? Miss Wedderburn, without any given reason, says that Dean is innocent. Prain is of the same way of thinking, and so am I. Parge alone seems to believe in Dean's guilt, and I don't agree with him. The man himself may be able to supply evidence to reveal the truth; but where is he to be found?"