"Still he might make an effort to save himself," thought Gebb, as he sat meditating in his office, "if only to tell a lie; although I don't quite see what he could say. Mrs. Presk declared that Miss Gilmar wore her jewels on that evening, and when we found the body those jewels were gone. The principal jewel--which is a necklace--was pawned the day after the murder by Arthur Ferris, who knows Miss Wedderburn, who knew Miss Gilmar; and he refuses to state how the necklace came into his possession. If he murdered the woman his possession of the diamonds is easily accounted for: if he is innocent he must have obtained the necklace from the assassin. Therefore, if not guilty himself, he must know who is: that is plain logic." Logic or not, the result of the argument was very unsatisfactory, and Gebb, in his own mind, was unable to decide either for or against Ferris. He had that morning informed Prain by letter about the artist's committal for trial, and asked him to call at the prison to discover if possible the reason for the strange conduct of Ferris. Also, he requested Prain to call at his office, and tell him the result of the interview. So when his meditations were interrupted by a sharp knock at the door, he quite expected to see the little solicitor enter. In place of Prain, however, he beheld the burly form of John Alder, who appeared to be different from his usual genial self. "You are no doubt surprised to see me here, Mr. Gebb," he said, when the first greetings had passed, "but I am greatly disturbed about Ferris. He is a friend of mine, you know." Gebb did not know about the friendship, but he was well aware that Ferris was Alder's favoured rival with Edith Wedderburn, so wondered at the tender-heartedness of the man who was distressed over the removal of an obstacle to his wooing. "Why are you disturbed?" asked Gebb, rather sceptically. "What makes you worry over Ferris?" "Because I am sure he is innocent of this murder," replied Alder. "Oh, I heard all about his arrest and committal for trial from Prain, who has gone round to see him. So I thought I would come and tell you that I am convinced of his innocence." "But he pawned the necklace, Mr. Alder; he admits that he did." "Then he must have obtained the necklace from some one else." "That may be, sir," said Gebb, quietly; "but if he did he refuses to say as much. And whosoever gave him the necklace killed Miss Gilmar." "What defence does he make?" asked Alder, looking puzzled. "None. He asserts his innocence, but refuses to explain how he became possessed of the necklace. If he can't explain, or won't explain, those diamonds will hang him." "In what way? I don't quite see how you arrive at that point." "Miss Gilmar wore the necklace on the night she was killed," explained the detective; "it was gone when we found the body; so by the strongest of circumstantial evidence the assassin must have taken it."