"I'm going to Hertford to see Miss Rider's mother; and incidentally, I may pick up Miss Rider, who is very likely to have gone home." Whiteside nodded. "What do you expect to find out from the mother?" he asked. "I expect to learn a great deal," said Tarling. "There is still a minor mystery to be discovered. For example, who is the mysterious man who comes and goes to Hertford, and just why is Mrs. Rider living in luxury whilst her daughter is working for her living at Lyne's Store?" "There's something in that," agreed Whiteside. "Would you like me to come along with you?" "Thanks," smiled Tarling, "I can do that little job by myself." "Reverting to Milburgh," began Whiteside. "As we always revert to Milburgh," groaned Tarling. "Yes?" "Well, I don't like his assurance," said Whiteside. "It looks as if all our hopes of getting a clue from the examination of Lyne's accounts are fated to be dashed." "There's something in that," said Tarling. "I don't like it myself. The books are in the hands of one of the best chartered accountants in the country, and if there has been any monkey business, he is the fellow who is certain to find it; and not only that, but to trace whatever defalcations there are to the man responsible. Milburgh is not fool enough to imagine that he won't be found out once the accountants get busy, and his cheeriness in face of exposure is to say the least disconcerting." Their little conference was being held in a prosaic public tea-room opposite the House of Commons--a tea-room the walls of which, had they ears, could have told not a few of Scotland Yard's most precious secrets. Tarling was on the point of changing the subject when he remembered the parcel of books which had arrived at the accountant's office that morning. "Rather late," said Whiteside thoughtfully. "By Jove! I wonder!" "You wonder what?" "I wonder if they were the three books that Milburgh bought yesterday?" "The three ledgers?" Whiteside nodded. "But why on earth should he want to put in three new ledgers--they were new, weren't they? That doesn't seem to me to be a very intelligent suggestion. And yet----" He jumped up, almost upsetting the table in his excitement. "Quick, Whiteside! Get a cab while I settle the bill," he said. "Where are you going?" "Hurry up and get the cab!" said Tarling, and when he had rejoined his companion outside, and the taxi was bowling along the Thames Embankment: "I'm going to St. Mary Axe." "So I gathered from your directions to the cabman," said Whiteside. "But why St. Mary Axe at this time of the afternoon? The very respectable Dashwood and Solomon will not be glad to see you until to-morrow." "I'm going to see these books," said Tarling, "the books which Milburgh sent to the accountants this morning." "What do you expect to find?" "I'll tell you later," was Tarling's reply. He looked at his watch. "They won't be closed yet, thank heaven!"