"There is the envelope," he said. "Nothing but _Mr. Cave_, as you see--that is also typewritten." Miss Penkridge picked up the envelope as Mr. Cave tossed it across the table. She appeared to examine it carefully, but suddenly she turned to Mr. Carless. "There _is_ a clue in these things!" she exclaimed. "A plain clue! One that's plain enough to me, anyway. I could follow it up. I don't know whether you gentlemen can." Mr. Carless, who had, up to that point, treated Miss Penkridge with good-humoured condescension, turned sharply upon her. "What do you mean, ma'am?" he asked. "You really see something in--in a typewritten letter?" "A great deal!" answered Miss Penkridge. "And in the stationery on which it's typed, and in the envelope in which it's inclosed. Now look here: This letter has been typed on a half-sheet of notepaper. Hold the half-sheet up to the light--what do you see? One half of the name and address of the stationer who supplied it, in watermark. What is that one half?" Mr. Carless held the paper to the light and saw on the top line, ... "_sforth,"_ on the middle line, ... "_nd Stationer_" and, ... "_n Hill_" on the bottom line. "My nephew there," went on Miss Penkridge, "knows what that would be, in full, if the other half of the sheet were here. It would be precisely what it is under the flap of this envelope--there you are! '_Bigglesforth, Bookseller and Stationer, Craven Hill.'_ Everybody in this district knows Bigglesforth--we get our stationery from him. Now, Bigglesforth has not such a very big business in really expensive notepaper like this--the other half of the sheet, of course, would have a finely engraved address on it--and you can trace the owner of this paper through him, with patience and trouble. "But here's a still better clue! Look at this typewritten letter. In it, the letter _o_ occurs with frequency. Now, notice--the letter is broken, imperfect; the top left-hand curve has been chipped off. Do you mean to tell me that with time and trouble and patience you can't find out to whom that machine belongs? Taking the fact that this half-sheet of notepaper came from Bigglesforth's, of Craven Hill," concluded Miss Penkridge with emphasis, "I should say that this document--so important--came from somebody who doesn't live a million miles from here!" Mr. Carless had followed Miss Penkridge with admiring attention, and he now rose to his feet. "Ma'am," he exclaimed, "Mr. Viner's notion of having you to join our council has proved invaluable! I'll have that clue followed up instantly! Gentlemen, we can do no more just now--let us separate. Mr. Cave--you'll continue to be heard of at the Belfield Hotel?" "I shall be at your service any time, Mr. Carless," responded Mr. Cave. "A telephone message will bring me at once to Lincoln's Inn Fields." The assembly broke up, and Viner was left alone with Miss Penkridge.