"It is not in his other pocket-books," declared Rhona. "I went through all his things myself very early this morning—through everything that he had here. I know that he had that envelope yesterday—he pulled out some things from his pocket when we were lunching with Mr. Kenthwaite in a restaurant in Fleet Street, and I saw the envelope. It was a stout, square envelope, across the front of which he had drawn two thick red lines, and it was heavily sealed with black sealing-wax at the back."
"That was yesterday, you say?" asked Matherfield sharply. "Yesterday noon? Just so! Then as he had it yesterday at noon, and as it wasn't in his pockets last night and is not among his effects in this house, it's very clear that between, say, two o'clock yesterday and midnight he parted with it. Now then, to whom? That's a thing we've just got to find out! But you're sure he wasn't joking when he told you that this discovery, or invention, or whatever it was, was worth a potential fortune?"
"On the contrary, he was very serious," replied Rhona. "Unusually serious for him. He wouldn't tell me what it was, nor give me any particulars—all he said was that he'd solved a problem and hit on a discovery that he'd worked over for years, and that the secret was in that envelope and worth no end of money. I asked him what he meant by no end of money and he said: 'Well, at any rate, a hundred thousand pounds—in time.'"
The two men exchanged glances; silence fell on the whole group.
"Oh!" said Matherfield at last. "A secret worth a hundred thousand pounds—in time. This will have to be looked into—narrowly. What do you think, Mr. Hetherwick?"
"Yes," answered Hetherwick. "You've no idea, of course, as to whether your grandfather had done anything about putting this discovery on the market—or made any arrangement about selling it? No! Well, can you tell me this: What sort of house did your grandfather want to rent here in London? I mean, do you know what rent he was prepared to pay?"
"I can answer that," remarked Mrs. Keeley. "He told me he wanted a good house—a real good one—in a convenient suburb, and he was willing to go up to three hundred a year."
"Three hundred a year," said Hetherwick. He exchanged a meaning glance with Matherfield. "That," he added, "looks as if he felt assured of a considerable income, and as though he had already realised on his discovery or was very certain of doing so."
"To be sure," agreed Matherfield. "Of course, I don't know what his private means were, but I know what his retiring pension would be—and three hundred a year for rent alone means—a good deal! Um!—we'll have to endeavour to trace that sealed envelope."
"It seems to me, Matherfield," observed Hetherwick, "that the first thing to do is to trace Hannaford's movements last night, from the time he left this hotel until his death in the train."