"You're talking in parables, like a detective out of a book," said Thornton, with a peevishness that his covering smile could not entirely conceal. "But I know you'll have your own way when you don't want to be too precise. How do you regard the burnt paper? Is it important?" "It would have been if I could have saved it," said the detective regretfully. "As it is, it's of no use as evidence in a court, for it only rests on my word. I keep pegging away at it, but I'm not certain that I can fill it out as it should be. But you never know your luck in our trade. I remember a case of forgery once. The counterfoil of a tradesman's paying-in book showed £100 with which he was not credited in the books of the bank. The cashier was confident that his initials in blue pencil on the counterfoil were genuine. Yet he was equally certain that he had not received the money. The tradesman was certain that he had sent the money. There it was. I was at a dead end. One day, I noticed a little stationer's store near the tradesman's office. In the window were some blue pencils. I walked in and bought something, and casually remarked that I shouldn't have thought there was much demand for those pencils. 'Oh, schoolboys buy 'em,' said the old woman who served me. 'There's old ----s' son over the way. He buys half a dozen at a time.' Well, off I went to the grammar school that the boy was attending, and had a talk with one of the masters. He admitted that the lad was exceptionally clever at drawing. I was beginning to see my way, so had the boy called out of his class into a private room. 'Now, tell me, my boy,' I said, 'what did you do with the money you stole from your father on such and such a date?' The bluff worked. He turned pale, and then admitted that he had forged the initials, taken the money, and gone on a joy-jaunt for a week while he was supposed to be staying with an aunt. There was the luck of the idea coming in my head through looking at those pencils." "Have you been looking at blue pencils to-day?" asked Thornton with interest. "Something of the kind," admitted Foyle with a smile, and before he could be questioned further had vanished. He had said nothing of the blotting-paper incident, for there were times when he wished to keep his own counsel even within the precincts of Scotland Yard itself. He did not wish to pin himself down until he was sure. In his own room, he unlocked the big safe that stood between the two windows, and taking out the roll he had abstracted from Lady Eileen's desk, surveyed it with a whimsical smile playing about the corners of his mouth. Once he held it to the mirror, and the word "Burghley" was plainly reflected. "That ought to do," he murmured to himself, and, replacing it in the safe, swung the heavy door to.