As he turned down Spring Street towards Sussex Square, Purdie hastily reviewed his knowledge of Mr. Spencer Levendale and his family. He had met them, only two months previously, at a remote and out-of-the-way place in the Highlands, in a hotel where he and they were almost the only guests. Under such circumstances, strangers are soon drawn together, and as Levendale and Purdie had a common interest in fishing they were quickly on good terms. But Purdie was thinking now as he made his way towards Levendale's London house that he really knew very little of this man who was evidently mixed up in some way with the mystery into which young Andie Lauriston had so unfortunately also become intermingled. He knew that Levendale was undoubtedly a very wealthy man: there were all the signs of wealth about him; he had brought several servants down to the Highlands with him: money appeared to be plentiful with him as pebbles are on a beach. Purdie learnt bit by bit that Levendale had made a great fortune in South Africa, that he had come home to England and gone into Parliament; that he was a widower and the father of two little girls--he learnt, too, that the children's governess, Miss Elsie Bennett, a pretty and taking girl of twenty-two or three, had come with them from Cape Town. But of Levendale's real character and self he knew no more than could be gained from holiday acquaintance. Certain circumstances told him by Melky about the rare book left in old Multenius's parlour inclined Purdie to be somewhat suspicious that Levendale was concealing something which he knew about that affair--and now here was Miss Bennett writing what, on the face of it, looked like an appealing letter to him, as if something had happened.

Purdie knew something had happened as soon as he was admitted to the house. Levendale's butler, who had accompanied his master to the Highlands, and had recognized Purdie on his calling the previous day, came hurrying to him in the hall, as soon as the footman opened the door.

"You haven't seen Mr. Levendale since you were here yesterday, sir?" he asked, in a low, anxious voice.

"Seen Mr. Levendale? No!" answered Purdie. "Why--what do you mean?"

The butler looked round at a couple of footmen who hung about the door.

"Don't want to make any fuss about it, Mr. Purdie," he whispered, "though it's pretty well known in the house already. The fact is, sir, Mr. Levendale's missing!"

"Missing?" exclaimed Purdie. "Since when?"

"Only since last night, sir," replied the butler, "but the circumstances are queer. He dined out with some City gentlemen, somewhere, last night, and he came home about ten o'clock. He wasn't in the house long. He went into his laboratory--he spends a lot of time in experimenting in chemistry, you know, sir--and he called me in there. 'I'm going out again for an hour, Grayson,' he says. 'I shall be in at eleven: don't go to bed, for I want to see you for a minute or two.' Of course, there was nothing in that, Mr. Purdie, and I waited for him. But he never came home--and no message came. He never came home at all--and this morning I've telephoned to his two clubs, and to one or two other places in the City--nobody's seen or heard anything of him. And I can't think what's happened--it's all so unlike his habits."

"He didn't tell you where he was going?" asked Purdie.

"No, sir, but he went on foot," answered the butler. "I let him out--he turned up Paddington way."

"You didn't notice anything out of the common about him?" suggested Purdie.

The butler hesitated for a moment.

"Well, sir," he said at last, "I did notice something. Come this way, Mr. Purdie."

Turning away from the hall, he led Purdie through the library in which Levendale had received Ayscough and his companions into a small room that opened out of it.

Purdie, looking round him, found that he was standing in a laboratory, furnished with chemical apparatus of the latest descriptions. Implements and appliances were on all sides; there were rows of bottles on the shelves; a library of technical books filled a large book-case; everything in the place betokened the pursuit of a scientific investigator. And Purdie's keen sense of smell immediately noted the prevalent atmosphere of drugs and chemicals.

"It was here that I saw Mr. Levendale last night, sir," said the butler. "He called me in. He was measuring something from one of those bottles into a small phial, Mr. Purdie--he put the phial in his waistcoat pocket. Look at those bottles, sir--you'll see they all contain poison!--you can tell that by the make of 'em."

Purdie glanced at the shelf which the butler indicated. The bottles ranged on it were all of blue glass, and all triangular in shape, and each bore a red label with the word Poison prominently displayed.

"Odd!" he said. "You've some idea?" he went on, looking closely at the butler. "Something on your mind about this? What is it?"

The butler shook his head.

"Well, sir," he answered, "when you see a gentleman measuring poison into a phial, which he carefully puts in his pocket, and when he goes out, and when he never comes back, and when you can't hear of him, anywhere! why, what are you to think? Looks strange, now, doesn't it, Mr. Purdie?"

"I don't know Mr. Levendale well enough to say," replied Purdie. "There may be some quite good reason for Mr. Levendale's absence. He'd no trouble of any sort, had he?"

"He seemed a bit upset, once or twice, yesterday--and the night before," said the butler. "I noticed it--in little things. Well!--I can't make it out, sir. You see, I've been with him ever since he came back to England-- some years now--and I know his habits, thoroughly. However, we can only wait--I believe Miss Bennett sent for you, Mr. Purdie?"

"Yes," said Purdie. "She did."

"This way, sir," said the butler. "Miss Bennett's alone, now--the children have just gone out with their nurses."

He led Purdie through the house to a sitting-room looking out on the garden of the Square, and ushered him into the governess's presence.

"I've told Mr. Purdie all about it, miss," he said, confidentially. "Perhaps you'll talk it over with him! I can't think of anything more to do--until we hear something."

Left alone, Purdie and Elsie Bennett looked at each other as they shook hands. She was a fair, slender girl, naturally shy and retiring; she was manifestly shy at renewing her acquaintance with Purdie, and Purdie himself, conscious of his own feelings towards her, felt a certain embarrassment and awkwardness.

"You sent for me," he said brusquely. "I came the instant I got your note. Grayson kept me talking downstairs. You're bothered--about Mr. Levendale?"

"Yes," she answered. Then she pointed to a chair. "Won't you sit down?" she said, and took a chair close by. "I sent for you, because--it may seem strange, but it's a fact!--I couldn't think of anybody else! It seemed so fortunate that you were in London--and close by. I felt that--that I could depend on you."

"Thank you," said Purdie. "Well--you can! And what is it?"

"Grayson's told you about Mr. Levendale's going out last night, and never coming back, nor sending any message?" she continued. "As Grayson says, considering Mr. Levendale's habits, that is certainly very strange! But--I want to tell you something beyond that--I must tell somebody! And I know that if I tell you you'll keep it secret--until, or unless you think you ought to tell it to--the police!"

Purdie started.

"The police!" he exclaimed. "What is it?"

Elsie Bennett turned to a table, and picked up a couple of newspapers.

"Have you read this Praed Street mystery affair?" she asked. "I mean the account of the inquest?"

"Every word--and heard more, besides," answered Purdie. "That young fellow, Andie Lauriston, is an old schoolmate and friend of mine. I came here yesterday to see him, and found him plunged into this business. Of course, he's absolutely innocent."

"Has he been arrested?" asked Elsie, almost eagerly.

"No!" replied Purdie. "He's gone away--to get evidence that those rings which are such a feature of the case are really his and were his mother's."

"Have you noticed these particulars, at the end of the inquest, about the book which was found in the pawnbroker's parlour?" she went on. "The Spanish manuscript?"

"Said to have been lost by Mr. Levendale in an omnibus," answered Purdie. "Yes! What of it?"

The girl bent nearer to him.

"It seems a dreadful thing to say," she whispered, "but I must tell somebody--I can't, I daren't keep it to myself any longer! Mr. Levendale isn't telling the truth about that book!"

Purdie involuntarily glanced at the door--and drew his chair nearer to Elsie's.

"You're sure of that?" he whispered. "Just so! Now--in what way?"

"It says here," answered Elsie, tapping the newspapers with her finger, "that Mr. Levendale lost this book in a 'bus, which he left at the corner of Chapel Street, and that he was so concerned about the loss that he immediately sent advertisements off to every morning newspaper in London. The last part of that is true--the first part is not true! Mr. Levendale did not lose his book--he did not leave it in the 'bus! I'm sorry to have to say it--but all that is invention on his part--why, I don't know."

Purdie had listened to this with a growing feeling of uneasiness and suspicion. The clouds centring round Levendale were certainly thickening.

"Now, just tell me--how do you know all this?" he asked. "Rely on me--to the full!"

"I'll tell you," replied Elsie, readily. "Because, about four o'clock on the afternoon of the old man's death, I happened to be at the corner of Chapel Street. I saw Mr. Levendale get out of the 'bus. He did not see me. He crossed Edgware Road and walked rapidly down Praed Street. And--he was carrying that book in his hand!"

"You're sure it was that book?" asked Purdie.

"According to the description given in this account and in the advertisement--yes," she answered. "I noticed the fine binding. Although Mr. Levendale didn't see me--there were a lot of people about--I was close to him. I am sure it was the book described here."

"And--he went in the direction of the pawnshop?" said Purdie. "What on earth does it all mean? What did he mean by advertising for the book, when--"

Before he could say more, a knock came at the door, and the butler entered, bearing an open telegram in his hand. His face wore an expression of relief.

"Here's a wire from Mr. Levendale, Miss Bennett," he said. "It's addressed to me. He says, 'Shall be away from home, on business, for a few days. Let all go on as usual.' That's better, miss! But," continued Grayson, glancing at Purdie, "it's still odd--for do you see, sir, where that wire has been sent from? Spring Street--close by!"