"Dr. Cortelyon!" she exclaimed. "Ah--I remember now. Mr. Ashton once told me, in quite a casual way as we were passing through the square, that he had known Dr. Cortelyon in Australia, years and years ago!" Drillford glanced at Viner and smiled. "I wish you'd remembered that little matter before, Miss Wickham!" he said. "It might have saved a lot of trouble. Well--Cortelyon's the man! And it all came about quite suddenly, this afternoon. Through your aunt, Mr. Viner--Miss Penkridge. Smart lady, sir!" "My aunt!" exclaimed Viner. "Why, how on earth--" "Some of your gentlemen had a conference with that fellow Cave at your house, after you left court this morning," said Drillford. "Miss Penkridge was present. Cave told more of his cock-and-bull story, and produced a certain letter which he said had been handed to him at the hotel he'd put up at. All that, and all the stuff he told at the police-court, was bluff--carefully concocted by himself and Cortelyon in case Cave was ever put in a tight corner. Now, according to what she tells me, Miss Penkridge immediately spotted something about that letter which none of you gentlemen were clever enough to see--" "I know!" interrupted Viner. "She saw that the envelope and paper had been supplied by Bigglesforth, of Craven Gardens, and that a certain letter in the typewriter which had been used was defective." "Just so," laughed Drillford, "and so, being, as I say, a smart woman, she went round to Bigglesforth, got him to herself, and made some inquiries. And--it's very queer, Mr. Viner, how some of these apparently intricate cases are easily solved by one chance discovery!--she hadn't been talking to Bigglesforth ten minutes before she was on the right track. Bigglesforth, when he'd got to know the main features of the case, was willing enough to help, and your aunt immediately brought him round here to see me. And I knew at once that we'd got right there!" "Yes--but how, exactly?" asked Viner. "Bigglesforth," answered Drillford, "told me that he'd supplied stationery to Dr. Cortelyon for some time, and he'd no doubt that the paper and envelope described by Miss Penkridge was some which he'd specially secured for the Doctor. But he told something far more important: Six months ago Cortelyon went to Bigglesforth and asked him if he could get him a good second-hand typewriter. Now, Bigglesforth had a very good one for which he'd no use, and he at once sold it to Cortelyon. Bigglesforth didn't mention the matter to his customer, for the machine was perfect in all other respects, but one of the letters was defective--broken. That was the same letter, Mr. Viner, which was defective in the document which Cave showed to you gentlemen and spoke of previously in court!" "Extraordinary!" muttered Viner. "What a piece of luck!"