Hewitt agreed that the affair had very uncommon features, and presently left the station and sought a cab. All the way back to his office he considered the matter deeply. As a matter of fact he was at a loss. Certain evidence he had seen in the house, but it went a very little way, and beyond that there was merely no clue whatever. There were features of the child’s first estrayal also that attracted him, though it might very easily be the case that nothing connected the two events. There was an unknown woman--apparently a lady--who had once had her throat cut, bringing the child back after several hours, and giving a false name and address, for since the address was false, the same was probably the case with the name. Why was this? This time the child was still absent, and nothing whatever was there to suggest in what direction he might be followed, neither was there anything to indicate why he should be detained anywhere, if detained he was. Hewitt determined, while awaiting any result that the bills might bring, to cause certain inquiries to be made into the antecedents of the Setons. Moreover, other work was waiting, and the Seton business must be put aside for a few hours at least. Hewitt sat late in his office that evening, and at about nine o’clock Mrs. Seton returned. The poor woman seemed on the verge of serious illness. She had received two anonymous letters, which she brought with her, and with scarcely a word placed before Hewitt’s eyes. The first he opened and read as follows:-- “The writer observes that you are offering a reward for the recovery of your child. There is no necessity for this; Charley is quite safe, happy, and in good hands. Pray do not instruct detectives or take any such steps just yet. The child is well and shall be returned to you. This I swear solemnly. His errand is one of mercy; pray have patience.” Hewitt turned the letter and envelope in his hand. “Good paper, of the same sort as the envelope,” he remarked, “but only a half sheet, freshly torn off, probably because the other side bore an address heading; therefore most likely from a respectable sort of house. The writing is a woman’s, and good, though the writer was agitated when she did it. Posted this afternoon, at Willesden.” “You see,” Mrs. Seton said anxiously, “she knows his name. She calls him ‘Charley.’” “Yes,” Hewitt answered; “there may be something in that, or there may not. The name Charles Seton is on the bills, isn’t it? And they have been visible publicly all day to-day. So that the name may be more easily explained than some other parts of the letter. For instance, the writer says that the child’s ‘errand’ is one of mercy. The little fellow may be very intelligent--no doubt is--but children of two years old as a rule do not practise errands of mercy--nor indeed errands of any sort. Can you think of anything whatever, Mrs. Seton, in connection with your family history, or indeed anything else, that may throw light on that phrase?”