The detective, who had already had several long conversations with Purdie at headquarters during the previous afternoon and evening, and knew him for a well-to-do young gentleman who was anxious to clear his friend Lauriston of all suspicion, shook his head. He was a quiet, sagacious, middle-aged man who evidently thought deeply about whatever he had in hand. "It's difficult to say, Mr. Purdie," he answered. "I've no doubt that when we get to the bottom of this case it'll turn out to be a very simple one--but the thing is to get to the bottom. The ways are complicated, sir--uncommonly so! At present we're in a maze--seeking the right path." "Do you think that this Parslett affair has anything to do with the Multenius affair?" asked Purdie. "Yes--undoubtedly!" answered the detective. "There's no doubt whatever in my own mind that the man who poisoned Parslett is the man who caused the old pawnbroker's death--none! I figure it in this way. Parslett somehow, caught a glimpse of that man leaving Multenius's shop--by the side-door, no doubt--and knew him--knew him very well, mind you! When Parslett heard of what had happened in Multenius's back-parlour, he kept his knowledge to himself, and went and blackmailed the man. The man gave him that fifty pounds in gold to keep his tongue quiet--no doubt arranging to give him more, later on--and at the same time he cleverly poisoned him. That's my theory, Mr. Purdie." "Then--the only question now is--who's the man?" suggested Purdie. "That's it, sir--who's the man?" agreed the detective. "One thing's quite certain--if my theory's correct. He's a clever man--and an expert in the use of poisons." Purdie walked on a minute or two in silence, thinking. "It's no use beating about the bush," he said at last. "Do you suspect Mr. Levendale--after all you've collected in information--and after what I told you about what his butler saw--that bottle and phial?" "I think that Levendale's in it," replied the detective, cautiously. "I'm sure he's in it--in some fashion. Our people are making no end of enquiries about him this morning, in various quarters--there's half-a-dozen of our best men at work in the City and the West End, Mr. Purdie. He's got to be found! So, too, has this man Stephen Purvis--whoever he is. We must find him, too." "Perhaps these letters that Melky Rubinstein speaks of may throw some light on that," said Purdie. "There must be some way of tracing him, somewhere."