Mr. Jacob Mason's house stood in its own grounds in a quiet suburban road. It was not a very large house, but it straggled about comfortably in the manner of detached houses built in the suburbs at a time when space was less valuable than now, and it consisted of two floors only. The front door was not far from the road, and was clearly visible to passengers who might chance to look through either of the two iron gates that opened one on each end of the semi-circular drive.

All these things Martin Hewitt noticed as the Rev. Mr. Potswood pushed open one of these gates, and the two walked up the drive. The front door stood in a portico, and a French window gave access to the roof of this portico from a bedroom or dressing-room. As Hewitt and his companion approached the house the French window was pushed open, and a man appeared—a middle-aged, slightly stoutish man with a short, grey beard; commonplace enough in himself, but now convulsed with noisy anger, shaking his fists and stamping on the portico-roof.

"Get out!" he shouted. "Don't come near my house again, or I'll have you flung out! Go away and take your friends with you! D'you hear? Go away, sir, and don't come here annoying me! Go! Go at once!"

Mr. Potswood absolutely staggered with amazement. "Why," he gasped, "it's Mason! He's mad—clean mad! Why, Mason, my poor friend, don't you know me?"

"Get out, I say!" cried Mason. "Give me no more of your talk! I won't have you here!" And now Hewitt caught a glimpse of a girl's face at the window behind the man—a pale and handsome face, drawn with anxiety and fear.

Hewitt seized the clergyman quickly by the arm. "Come," he whispered hurriedly, "come away at once. There is a reason for this. Get away at once. If you can answer back angrily, do so, but at any rate, come away."

He hurried back to the gate, half dragging the astounded rector, who was all too honest a soul to be able to counterfeit an anger he did not feel, even if his amazement had not made him speechless. Hewitt closed the gate behind him and said as he walked, "Where is the rectory? We will go there. He may have sent a message while you were out."

Mechanically the rector took the first turning. "But he's mad!" he protested. "Mad, poor fellow! Merciful heavens, Mr. Hewitt, his whole tale must have been a delusion! A mere madman's fancy! Poor fellow! We must go back, Mr. Hewitt—we really must! We can't leave that poor girl there alone with a raving maniac!"

"No," Hewitt insisted, "come to the rectory. That is no madness, Mr. Potswood. Couldn't you see the colour of the man under the eyes, and the shaking of his beard? That was not anger and it was not madness. It was terror, Mr. Potswood—sheer, sick terror! Terror, or some emotion very much like it."

"But, if terror, why that outburst? What does it mean? If it were terror, why not rather welcome our company and help?"

"Don't you see, Mr. Potswood?" answered Hewitt. "Don't you guess? Mason is watched, and he knows it! He was acting his anger before unseen eyes—and he knew they were on him!"

"God be merciful to us all," ejaculated the clergyman. "Poor man—poor sinner! What is this unspeakable thing which has him in its clutches? What had he done to give himself over to such a power?"

"We can tell nothing, and guess nothing, as yet," Hewitt answered. "Let us see if he has sent you a message. It seems likely. If he has it may help us. If not—then I think we must do something decisive at once. But don't hurry so! It is hard to restrain one's self, I know, but there may be eyes on us, Mr. Potswood, and we must not seem to be persisting in our errand."

So they went through the quiet streets for the two or three furlongs that seemed so many miles to the good parson. Arrived at the rectory, Mr. Potswood pushed impatiently through the gate, and was hurrying toward the house, when he perceived a bent little old man standing among some shrubs with his own gardener, who was digging.

"There's Mason's gardener!" the rector exclaimed, and went to meet him.

The old man touched his hat, looked sharply towards Hewitt, who was waiting near the rectory door, and then disappeared round a corner of the house, the rector following. In a few seconds Mr. Potswood reappeared, with a slip of paper in his hand. "Here," he said, "see this! The old man was told to give it to nobody but me, and in nobody else's presence. He's been waiting since one o'clock."

Scrawled on the paper, in trembling and straggling letters, were these words:—

"We must do as he says," remarked Hewitt. "We know nothing of this matter, and we must be guided till we do. Just write an unsigned note—'All shall be as you request,' or words to that effect, and be sure the man gives it to him. Let him out behind through the churchyard, if possible, and tell him not to go straight from one house to the other. Is he an intelligent man?"

"Yes—uncommonly shrewd, I believe. He says he can't have been followed. He knows several gardeners hereabout, and he seems to have called on each of them on his way—in at the front of the garden and out at the back each time, after a few minutes' conversation. Gipps is rather a cunning old fellow."

"Ah," said Hewitt admiringly, "that's the sort of messenger I often want. I'll give him half a crown for himself and the money to pay for a telegram on his way. He knows nothing essential, of course?"

"No—only that his master is in some sort of trouble, and warned him that he might be followed."

"That is good. I shall telegraph to Detective-Inspector Plummer, of Scotland Yard. All right—I quite understand that all I have heard is confidential. I shall tell Plummer nothing till I may—indeed, as yet I have very little to tell that would help him. But I think it will be well to have the police within call—we may want them at a moment's notice; I have no police powers, you see, and Plummer has the Denson case in hand. I will ask him to be here, at this house, before a quarter to eight, if you will allow me."

And so the telegram went to Plummer, and Hewitt, accepting the rector's invitation to an early dinner before starting on their visit, resigned himself to wait. He did not like the waste of time, as he frankly told Mr. Potswood. He would have preferred to see Mason at once, at any risk, and to take what means he thought necessary without delay. But as it seemed that the risk was to be chiefly Mason's, and as Mason knew all of which both he and the rector were ignorant, Mason must be allowed to choose his own time.

The excellent Mr. Potswood endured agonies of suspense, though he also insisted that Mason's wishes must be observed exactly. "What is it all—what can it be?" he ejaculated again and again. "What dreadful influence can thus compass a man about, here in London, in these times?"

It was autumn, and night fell early. Dinner was over at last, and they had scarcely left the table when Plummer arrived, anxious and eager.

"You'll have to trust me a little, Plummer," Hewitt said, when he had made him known to the rector. "I can tell you nothing now—know nothing, in fact, or very little more than nothing. The fact is, I'm going to see a man who promises information to me alone, in confidence, as his client, and I don't know how long I may have to keep you in the dark. But this is where the trail lies hot, and I know that's where you want to be. More, if you're wanted suddenly you'll be at hand. You have a man or two with you, I suppose, as I suggested?"

"Three of the best of them. They will follow us up. Is it far?"

"No, close enough. It is a house in a walled garden—not a high wall. We go in at a gate from the lane behind, and I think you should wait at that gate, and put your men at hand. We mustn't go in as a crowd. The rector had better go first, and you and I will follow on the opposite side of the road."

So the procession was formed, and it was still some three minutes short of eight o'clock when Hewitt and Plummer joined the clergyman at the door in the garden wall behind Mason's house. The door was ajar as had been promised in Mason's note. Leaving Plummer on guard without, Martin Hewitt and the rector stepped as silently as possible through the little kitchen garden and across a strip of lawn toward where a dull light illuminated the conservatory, at the right-hand end of the house. The door of the conservatory was ajar also, and this the rector pushed open.

"Miss Creswick!" the rector called, in a loud whisper. "Miss Creswick!" And with that a girl appeared within.

"Oh, Mr. Potswood," she said, "I'm so glad you've come! I can't think what's wrong with poor uncle! I'm afraid he must be going mad! He is terrified at something, and he has been getting worse, till he could hardly speak or walk. Dr. Lawson has been—about an hour ago, and since then uncle has been much quieter, in his study."

They were entering the dimly-lighted drawing-room now. "Dr. Lawson?" queried the rector. "Rather an unusual visitor, isn't he? How long has he been gone?"

Miss Creswick flushed slightly through all her paleness and grief. "I don't know," she said. "He let himself out, I fancy. He said he could not stay long when he came, but I didn't hear him go; I have been upstairs, and the servants are in the kitchen—they say uncle's mad, and I'm really afraid he is!"

They left the drawing-room, and walked along the corridor and the hall to the opposite side of the house, where the study lay. Miss Creswick tapped gently at the door, but there was no answer. She tapped again, louder, and then came the faint sound of a quick step on the carpet, and then a slight scraping noise, as when a door is closed over a carpet it will scarcely pass. "That's the window into the garden," said Miss Creswick. "Why is he going out? Uncle! Uncle Jacob!"

But now the silence was wholly unbroken. Hewitt snatched quickly at the door-handle. "Locked!" he said. "Come—the quickest way into the garden!"

They ran out at the front door, and round toward the study window. It was a French window, exactly at the opposite end of the house to the conservatory, and now the gas-light streamed out through one half of it, which stood curtainless and ajar, while the curtain was drawn across the other half. Hewitt was the least familiar with the place, but he was quickest on his legs, and more seriously alarmed than the others. He reached the window first—and instantly turned and thrust the rector back against Miss Creswick. "Quick! take her away," he said; "we are too late!" and in the same moment, even as Hewitt dashed over the threshold, he snatched a whistle from his pocket, and blew his hardest.

There on the floor lay Mason, his face dreadful and staring and black; tight in his neck was the band of a tourniquet, and fresh and wet on his forehead was the Red Triangle.

Hewitt snatched at the screw of the tourniquet behind the neck, and loosened it as quickly as hands could turn. But it was too late. Too late, the examining surgeon afterwards said, by a quarter of an hour.

Plummer was at the window with his men at his heels even before the tourniquet was half unscrewed.

"Round the wall of the garden," shouted Hewitt, "and whistle up the police! He's only this moment out!"

The house was alive with shouts and screams. The rector came running back, and Hewitt, busy with his useless attempt at restoration, called now for a doctor. People were scampering in the street, and Hewitt left the victim to the care of the rector, and himself joined Plummer, all in fewer seconds than it may be told in.

But Plummer and his men were beaten, for nothing—not so much as a moving shadow—was seen in the garden or about the walls. Worse, the general trampling would obliterate possible tracks. Plummer set a guard of police about the wall, and came in for consultation with Hewitt.

The body was carried into another room, and Hewitt and Plummer began an examination of the study.

"No signs of a struggle," commented Plummer, "and there was no noise, they say. That's very odd."

"From what I have seen and heard to-day," said Hewitt, "it is as I should have expected. I believe the man was almost killed by terror before he was strangled—dazed, stricken dumb, paralysed, deafened by it—everything but blinded, poor wretch. And to have been blinded would have been a mercy."

And then, as they made their examination systematically, calmly and without flurry, Hewitt told the whole tale of his day's adventures, together with all he had heard from the rector. "The man's dead," he said, "and his confidence is at an end. Indeed, I never had it—the case, so far as I am concerned, is over before I have even touched it. I haven't had a chance, Plummer; and the thing is deep and dark, deep and dark. Oh, if only the man had let me come to him in the daylight, spite of all! This might all have been averted.... There has been a close search here, too. See how everything is turned over. But, stay!"

A low fire smouldered in the grate, and on it lay ashes of many burnt papers. Hewitt passed the shovel carefully under these ashes, lifted them out and placed them gently on the table under the light of the gas-pendant.

"I must leave you," said Plummer. "There'll be an inspector here from the station in a moment—he won't interfere with you, and if anybody can get information out of this room it's you. The next thing for me is plain. I must make sure of Dr. Lawson, if he can be found."

"That is quite right, without a doubt," Hewitt responded. "I may find anything or nothing in this room, and, meanwhile, he was the last person known to have been here, and the only visitor, and he was not heard to go out, unless we heard him go when we were outside the study door. More, it was plainly some one familiar with the place who was able to get away so quickly by the window and the garden."

"And his interest in getting rid of Mason, too—the girl of age in a few months, and all obstacles to getting hold of her, and her money, removed. And—and the surgical tourniquet, the Chinese colour and everything!"

"Quite right, you must make sure of him, as you say. You will get his address from the rector. Meanwhile I'll try to begin my little contribution to the case—to begin it as best I can, after all the chances have made it useless."