“I can’t explain,” she said in a whisper.

“Does it matter?” her daughter asked. “As long as these people get their letters back again, what does it matter who they got them from?”

“They won’t get them; that is what matters,” the physician said gravely. “There is a criminal behind this advertisement. I must explain to you and to Mrs. Neobard, if she doesn’t know already, what these letters were about.”

Very deliberately and keeping his eyes fixed on the agitated woman all the time, Tarleton outlined the story of his discoveries. He was careful not to mention names. He explained why the doctor’s case-book had been taken from the safe, and why that precaution had proved useless. The dead man’s real hold over his victims had been through the letters he had persuaded them to write to him; those letters had been signed with a cipher, and the object of the advertisement was to make the writers disclose their identity so that they might be blackmailed by the holder of their secret confessions.

The widow’s distress became pitiable as the explanation proceeded. There could be no doubt that she was no party to the plot and hardly a doubt that its revelation had come to her as a complete shock. As for Sarah Neobard, her fine eyes fairly blazed with indignation.

“I never knew that such things were possible,” she exclaimed. “I don’t believe—I can’t believe—that my step-father ever meant to use the letters in such a way.”

At this point the consultant saw Mrs. Neobard open her eyes and look at him wistfully, as if to ask him to take no notice of her daughter’s tenderness for the scoundrel who had passed to his account.

“Surely you can’t think,” the girl pursued, “that my mother knew anything about this? Mother!”—she turned to the shrinking woman—“do you hear? You must do everything you can to help Sir Frank Tarleton to stop this iniquity.”

Now Sir Frank knew perfectly well that it could be stopped pretty easily by the simple step of Mrs. Neobard’s solicitors taking proceedings in her name for the recovery of the letters. The legal property in them, of course was vested in the writers, but until they claimed them the executrix was entitled to their possession; and if the Chancery Lane sharper refused to give them up or to disclose their whereabouts he was pretty sure to be struck off the Rolls and stood a good chance of being indicted for conspiracy. All this the adviser of the Home Office had known from the first, but he took care to keep the knowledge up his sleeve. For him the question of the letters was a secondary one and he was only using it as a means of opening the widow’s lips.

Miss Neobard suddenly stopped pleading with her mother to say to the specialist, “I think I can guess who has those letters—Madame Bonnell!”