"It can be done, with patience," said Brent. "It's got to be done. That handkerchief got into somebody's hands. That somebody is probably the murderer. As to how it can be traced--well, I suggest this. As far as I'm conversant with laundry matters, families, such as Mrs. Marriner says she works for, have laundry books. These books are checked, I believe, when the washing's sent home. If there's an article missing, the person who does the checking notes it; if a wrong article's enclosed, that, too, is noted, and returned to the laundry." "If Wellesley's handkerchief got to the wrong place, why wasn't it returned?" demanded Hawthwaite. "To be sure; but that's just what you've got to find out," retorted Brent. "You ought to go to Mrs. Marriner's laundry and make an exhaustive search of her books, lists, and so on till you get some light--see?" "Mrs. Marriner has, I should say, a hundred customers," remarked Hawthwaite. "Don't matter if Mrs. Marriner's got five hundred customers," said Brent. "That's got to be seen into. If you aren't going to do it, I will. Whoever it was that was in that Mayor's Parlour tried to burn a blood-stained handkerchief there. That handkerchief was Wellesley's. Wellesley swears he was never near the Mayor's Parlour. I believe him! So that handkerchief got by error into the box or basket of some other customer of Mrs. Marriner. Trace it!" He rose and moved towards the door, and Hawthwaite nodded. "We'll make a try at it, Mr. Brent," he said. "But, as I say, to work on a slight clue like that----" "I've known of far slighter clues," replied Brent. Yet, as he went away, he reflected on the extreme thinness of this clue--it was possible that the handkerchief had passed through more hands than one before settling in those of the person who had thrown it on the hearth, stained with Wallingford's blood, in the Mayor's Parlour. But it was a clue, and, in Brent's opinion, _the_ clue. One fact in relation to it had always struck him forcibly--the murderer of his cousin was either a very careless and thoughtless person or had been obliged to quit the Mayor's Parlour very hurriedly. Anyone meticulously particular about destroying clues or covering up traces would have seen to it that the handkerchief was completely burnt up before leaving the room. As it was, it seemed to Brent that the murderer had either thrown the handkerchief on the hearth, seen it catch fire and paid no more attention to it--which would denote carelessness--or had quitted the place immediately after flinging it aside, which would imply that some sound from without had startled him--or her. And, was it him--or was it her? There were certain features of the case which had inclined Brent of late to speculating on the possibility that his cousin had been murdered by a woman. And, to be sure, a woman was now in the case--Mrs. Mallett. If only he knew why Mrs. Mallett went to see the doctor and the Mayor....