The Professor, leaning forward on his walking-cane, and the detective, watching the woodman with a sharp side-glance, alike felt that they were on the verge of a revelation. But Blick’s brain was busy with a queer, confused doubt. Roper talked of guesswork, and it was not guess-work that Blick wanted; he was wondering what Roper meant by guess-work. And yet—for all they knew, they might at that instant be within tangible distance of the much-wanted truth.

“Well?” he said. “Well? What is it?”

“Seems little enough when you come to tell of it, like—and I’m no great hand,” replied Roper. “But—this here! Last Monday night it was—night afore Guy Markenmore was found, beyond there, at Markenmore Hollow. That night, after I’d had my supper, I left my cottage to walk to Mitbourne—there was a man there as I wanted to see. I took up the hill-side, just behind Woodland Cottage, and struck into that grass-track that run a-top of the downs from thereabouts to near Mitbourne Station. And I might ha’ been about a mile or so along that when I hears men a-coming towards me——”

“What time was that, Roper?” interrupted Blick.

“It ’ud be about a quarter-past eight, and nicely dark. Now, I’d reasons o’ my own for not wanting to be seen going Mitbourne way, so when I hears they men a-coming along, I slips behind a big clump o’ gorse that was handy, and stands still. Bimeby, these two comes walking closer—I see ’em outlined against the grey o’ the sky over Selcaster way, d’ye see. One tall man—one shortish man. A few yards away, the tallish man pulls up and lights a cigar. I see his face in the light o’ the match. Then you might ha’ knocked me down with a feather, for ’twas the man I hadn’t never stopped thinking about for seven bitter years, and you may reckon who that was—Guy Markenmore! I see him so well—just for a minute—as I do see you; no mistaking of him, for there wasn’t as much alteration in his face, damn him! as what I do allow he’d ha’ seen in mine. There he was, and if it hadn’t been for t’other with him, I’d ha’ gone for him there and then. But—I didn’t! They come on, talking, they hadn’t never stopped talking since I first see ’em——”

“Hear what they said?” asked Blick.

“Not to remember—only words here and there. Until they come right opposite me—then, as they walks past, I hears something distinct enough. Guy Markenmore, he say it—‘I shall be coming along here about four o’clock in the morning to catch the four something from Mitbourne for Farsham,’ he say, and then he laughs. ‘You’ll be safe and snoring in your bed,’ he say, ‘at that time, no doubt.’ ‘Don’t you be too sure!’ say the little fellow. ‘I’m as early a bird as there is when I’m in the country!’ Then they go on, Markenmore way, and I see ’em disappears round the corner of a spinney that stands about there. And then—”

“A moment, Roper,” interrupted Blick. “The second man—the littlish chap you describe. Did he talk like a countryman? Like anybody about here, you know?”

“No!” replied Roper with emphasis. “Not he! London way o’ talking, his. Wasn’t nobody belonging to these here parts, I know. I been in London, to my sorrow! A Londoner, I set he down for.”

“You didn’t see his face?”

“I didn’t see nothing of he, ’cepting his figure, like. He stand away, as it were, out o’ the light when Guy was a-lighting of his cigar, so I didn’t catch nothing, of his looks. But he was a littlish, broadish chap. To be sure, I didn’t take no great notice of he—’cause I was wishing he wasn’t there at all!”

“Well—what then?” asked Blick.

“Then I goes on to Mitbourne and do my business with the man as I wanted to see,” said Roper, “and when that was done, I had a pint o’ ale with him at the Cock and Pie, and so come home again.”

“Aye,” remarked Blick. “Just so! And——” he paused and gave Roper a particularly knowing look. “Anything else?” he asked.

“I ain’t a-going to keep nothing back,” said Roper. “There is something else. Don’t ’ee forget as how I’d been keeping my feelings warm for Guy Markenmore for seven years! A man what’s been wronged as I had, he don’t forget easy. And when I gets to my cottage, all alone, that night, after I come in from Mitbourne, I sat a-thinking. And I did remember—’cause I hadn’t forgotten!—what Guy say to that chap he was with, about being on that footpath to Mitbourne at four o’clock next morning. So I gets up at three o’clock and sets off to meet him, intending, if I did find him up there, to have it out wi’ he—once for all!”

“Did you find him?” asked Blick quietly.

Roper glanced from the detective to the Professor.

“Aye!” he answered equally quietly. “I found him! But there’d been somebody there before me. He was warm, then—but dead enough, wi’ a bullet through the brain!”

The Professor gave a little sigh. But Blick showed no sign of surprise, and his voice, when he spoke, was more matter-of-fact than ever.

“It had happened, then, just before you got there?” he said. “See anybody about?”

Roper shook his head.

“When I found him,” he replied, “I made out as how he’d shoot his-self. But I looked close and sharp all about him, and I see there wasn’t no weapon—no pistol, revolver, nothing o’ that sort. Then I looks all round—I see nobody! It was grey morning, and you couldn’t see very far; there was mists amongst the spinneys and coppices, and curling along, the tops o’ the downs. No, I see nobody—’cepting hisself, dead.”

“Did you touch him?” enquired Blick suddenly.

A curiously dark look came over the woodman’s face, and now he looked, not at the detective, but at the Professor, as if he felt that in him he was secure of a certain sympathy and understanding.

“It’s a queer thing,” he muttered, “but a minute before I come across him, there’s nothing I could ha’ liked better than to lay hands on he! I’d ha’ had him by the throat and shook the life out of him same as that there dog ’ud shake it out of a rat! But when I see him lying there at my feet, dead and gone, I felt—I felt as if I couldn’t bide to touch a hand to his body! He was—dead! And yet I did a thing, and it was through doing that I came to know that he was still warm.”

“Yes—yes!” breathed the Professor. “What, now?”

“I see a ring on his finger,” answered Roper simply. “The sort o’ ring that they gipsy women do trade off on the lanes hereabouts: a thing o’ no vally, you understands, but one that you’d notice. And it come on me—I dunno why—that my Myra had given it to him. And I pulled it off his finger, and I went away wi’ it, leaving him there, a-staring at the sky!”

The Professor let out a long sigh. But Blick spoke.

“What have you done with that ring, Roper?” he asked.

“’Tis here!” said Roper, putting two fingers in his waistcoat pocket. “’Tis in my mind that my poor lass gave it to he! Her was fond o’ gew-gaws o’ that sort. Many’s the time her’d been took in by they gipsy-women, trading a bit o’ poor trash o’ that sort to her for good money. But it’s in me to think ’twas hers, and I wasn’t going to let he carry that to his grave!”

“Well, you were wrong,” said Blick, with remorseless candour. “Mrs. Tretheroe gave that ring to Guy Markenmore, and he gave Mrs. Tretheroe another exactly like it. They bought them in an old curiosity shop on Portsmouth Hard. It was never Myra’s.”

Roper looked fixedly at the detective. Blick nodded. And at that Roper, who had been turning the ring over in the palm of his hand, suddenly threw it on the ground before him with a gesture of dislike.

“I had thought it med be!” he muttered. “But since it isn’t——”

Blick picked up the ring and rose to his feet.

“Now, Roper,” he said, “that’s the whole truth?”

“All I know,” answered Roper. “Can’t say one word more, master.”

“You’ll stand by it?” demanded Blick.

“Stand by every word I’ve said,” affirmed Roper.

“It comes to this,” continued the detective, turning to the Professor. “We’ve heard now of a man who was in Guy Markenmore’s company the evening before the murder, and who knew that Guy would be on the downs at four o’clock next morning. Who is that man?”

“Probably the man his clerk told me about,” answered the Professor. “That’s my opinion, anyway.”

“Well, let’s be going,” said Blick. “I’ll see you again, Roper—you’ve no doubt put us on the track of something.”

But the Professor lingered.

“Look here, my man,” he said, turning to the woodman. “You know the Mitre Hotel, at Selcaster? Very good—I’m staying there. Come and see me there, tonight; there’s my card—ask for me. If you want to emigrate I’ll find you the money. Tonight, mind, any time you like after eight o’clock.”

He nudged Blick’s elbow and hurried him away out of the wood before Roper could thank him, walking at a great pace until he and his companion were once more on the hill-side.

“There’s a man into whose soul the iron has entered, my friend!” he said. “Poor fellow! poor fellow! I feel deeply and sincerely sorry for him. Seven years lonely brooding over his love affair—terrible!”

“I fear you have a very deep vein of sentiment, sir!” observed Blick. “I’m sorry for the chap, too; he evidently took Myra’s defection pretty badly to heart. But I’ll tell you what I think, Professor—I think Master Roper ought to be feeling very thankful that I didn’t request him to march down to Selcaster police-station with me! If I were not a believer in psychology as a science I should certainly have desired his presence there. But I sized him up, and watched him closely, and I think I understand his curious mental processes, and I believe he told us the truth. I only wish he’d come and confided in me a week since!”

“Do you know, I rather think that I should have done precisely what he did, had I been in his case?” remarked the Professor ingenuously. “I sympathized with the unhappy man all through. But now, my dear fellow—this mysterious person? How are you going to get on his trail?”

“The queer thing about that,” observed Blick, “is this—at least, it’s a surface difficulty. Taking Roper’s story to be true—as I do—here’s a strange man, a Londoner by his speech, says Roper, by which he probably means a man of the educated classes, on the downs with Guy Markenmore, late on Monday evening. Who is he? Did he come down with Markenmore from London? Did they meet in the train? Did they foregather on the way between Mitbourne and Markenmore? We don’t know. But there are more important questions than any of these—for one, where was that man going? Where did he go when he and Markenmore parted?—for another. And for a third, and most important one—if he’s the man who shot Guy Markenmore next morning, where had he been in the meantime? Where did he spend Monday night? It couldn’t have been far away from hereabouts, if he laid in wait for his victim at four o’clock next morning!”

“Puzzling!” admitted the Professor. “Yet I suppose that a man who had much at stake wouldn’t mind sticking it out in these woods for a few hours—the nights are warm now, and there’s a lot of shelter here, in these valleys. Now, what amazes me is—if this man murdered Guy Markenmore, as I’m sure he did, why didn’t he murder him on Monday night and get away in the darkness?”

Blick laughed.

“I’ll tell you why,” he answered. “He was a man whom Guy Markenmore had taken into his confidence about this dye affair. He had come down with him, fully acquainted with what Guy was doing. He knew that the money business was likely to be settled that night. And he waited until morning so that he could possess himself of the cash as well as the formula you have told us of—with your opinion attached to it. Probably he is the man of whom Markenmore’s clerk at Folgrave Court told you, and we’ll have to try and find him. But the clue’s thin and poor, so far.”

The Professor nodded, paused, and looked about him. While talking, they had strolled slowly along the hill-side into a still wilder stretch of country. They were now standing on the edge of a deep ravine, which cut into the land beneath to a depth of some two hundred feet; here and there the fall was precipitous; in the dark and gloomy recesses far below great masses of yew and pine were broken by huge blocks of grey limestone; over everything hovered a sombre and mysterious silence. But suddenly the Professor broke it.

“There is somebody signalling to us!” he exclaimed. “Down there! A woman!”

Blick looked in the direction indicated, and started in surprise. Far away below them, a little to their right, he saw a woman’s figure standing near a grove of trees which lay at the foot of the most precipitous part of the ravine. And, as the Professor said, she was certainly endeavouring to attract their attention.

“Good Heavens!” he said. “That’s Miss Valencia Markenmore! Whatever is she doing down there? Do you know what they call this place?—the Devil’s Grip! Grip, I suppose, means a sharp cut in the surface of the land. But what can she want?”

“Let us make our way down,” suggested the Professor. “We are evidently wanted. Hello! there are men, too!”

Two figures had just emerged from amongst the cluster of pine trees near which Valencia stood. Blick suddenly recognized them as those of Harborough and Mr. Fransemmery. They, recognizing the detective, also began signalling to him.

“There’s something afoot down there!” he muttered. “Looks to me as if they’d made some discovery. Look here, sir!—that tall man is Harborough, who, as I told you, was accused of the murder by Mrs. Tretheroe; the other is Mr. Fransemmery, the old gentleman who has figured in the case.”

“I know Fransemmery by name,” replied the Professor. “He’s a member of an archaeological society to which I also belong—I’ve corresponded with him. Now, how can we get down there without breaking our necks.”

“There’ll be a sheep-track somewhere along here,” said Blick. “Where a sheep can go, we can—at a pinch.”

But some minutes passed before they found a means of descending into the depths of the ravine wherein the others there awaited their coming. Once in its recesses the Professor wondered at the precipice-like character of the cliff down which they had made their way. Above the spot at which Valencia and her two companions were standing, the granite walls rose high and cliff-like; at one place there was a sheer drop of two hundred feet, terminating in a wild and broken mass of rock and shrub; it was at the lower edge of this wilderness that the three stood, looking alternately into its recesses and at the men hurrying along the level floor of the ravine towards them. At Mr. Fransemmery’s heels, held in a leash made out of his master’s handkerchief, the Airedale terrier fretted and whimpered, evidently desirous of once more penetrating into the gorse bushes from whence he had been unceremoniously dragged.

“That’s Fransemmery’s dog—the chap that unearthed the automatic pistol!” said Blick. “I wonder if he’s made another discovery?”

Harborough came slowly towards them. As he approached he gave Blick a warning look and pointed to the pine trees.

“I say!” he said in a hushed voice, as they drew near. “There’s a man lying dead in there!—he must have fallen over the cliff. The terrier found him—we couldn’t get him away, so I went in for him and saw this man—dead, I say. Come and see!”

They were up to the other two by that time, and Blick, without further question or any ceremony, plunged in amongst the trees, followed by the three men.

“Where is he? Who is he?” he asked. “Anybody you know?”

“A stranger—looks like a tourist,” said Harborough. “Here, at the foot of the rocks!”

He thrust and held aside the clinging branches of the pines, and suddenly revealed the body of a man, lying in a curiously twisted attitude across a mass of sharp-edged stone. One glance upward was sufficient to show what had befallen him; he had slipped from the edge of the precipice far above, and crashed without a break, on the place where he lay: a little distance from him lay the walking-stick which he had dropped from his hand as he fell.

With a sharp exclamation Blick sprang forward and turned the face, hitherto crushed in amongst a cushion of moss and heather, to the light. He rose, staring at it.

“Good God!” he said. “It’s Crawley—the man I met——”

But a stronger, far more astonished exclamation came from the Professor, as he in his turn saw the dead man’s face.

“Crawley?” he said. “Crawley? Man alive!—That’s Carter! Carter! Carter, I tell you!”

Blick felt as if an ice-cold wave of illumination had washed across his brain. He turned on the Professor with searching eyes.

“Carter!” he exclaimed. “Your assistant?”

“My assistant!”

“The man who carried your sealed letter to Guy Markenmore?”

“That very man!” affirmed the Professor solemnly. “Good Lord! What does all this mean?”

Blick suddenly dropped on his knees by the dead man’s side and abruptly plunged a hand into an inner pocket of the clothing—into a second—a third. Just as suddenly he produced a letter-case, and from it drew out a wad of bank-notes and two papers. He dropped the notes unconcernedly on the stones, and hastily unfolded the papers; a second later he thrust these into the Professor’s hand.

“That’s what it means!” he said quietly. “There’s Spindler’s formula, and there’s your opinion about it. And—this is the chap who killed Guy Markenmore!”

Then he looked round at the three men. The Professor was staring blankly at the papers just handed to him; Mr. Fransemmery was staring at the Professor; Harborough, anxious and puzzled, was looking doubtfully at the dead man. It was he who spoke first, turning to the detective.

“You think he—that he killed Guy Markenmore in order to get possession of—those?” he asked, in a low voice.

Blick rose from his knees.

“What else?” he said calmly. “I see the whole thing now! Sir Thomas, there, and I already know something of it, but up to a few minutes ago I didn’t suspect this man. But, as I say, now I see it—clearly enough. This man, whom I met a few nights ago at the Sceptre, posing as Crawley, a holidaymaker, taking a walking tour round this country, is in reality Carter, an assistant of Sir Thomas’s at his laboratory at Cambridge. It was he to whom Sir Thomas entrusted a sealed packet for direct conveyance to Guy Markenmore in London; he, Carter, was passing through London on his way here for his holiday. Now, although Carter did not know the nature of the precise contents of that packet, he had learnt from Sir Thomas that they were of immense scientific and monetary value. He was charged to put the packet into Guy Markenmore’s own hands. He did so. Later that day Guy Markenmore travelled down here. So did Carter. Probably they met on the train; probably they travelled in company. But, at any rate, Sir Thomas and I have just found out that Guy Markenmore and Carter were together on these downs late that night, talking confidentially. Now from what I’ve learned about him, Guy Markenmore was a talkative, free-and-easy sort of a man, open and candid; probably, knowing that Carter was Sir Thomas’s assistant, Guy took Carter into his confidence about the secret. And Sir Thomas and I have just ascertained that Guy told Carter that he would be at or about Markenmore Hollow at a very early hour next morning. What does Carter do? He forms the plan of hanging about all night—a warm night, mind!—waylaying Guy early in the morning and murdering him for the secret and for the money which was to be put together for it that night by Guy, Lansbury, and Baron von Eckhardstein. And—he carries all this into execution. What does he do, then? Goes quietly away amongst these hills and woods on his walking-tour—who’s going to suspect an innocent-looking pedestrian? But, having in the meantime read the newspapers, he works round, in his character of tourist, to the Sceptre, where I met him, and where, I confess, he thoroughly took me in. The murderer’s old trick, you see, of hanging round the scene of his crime, full of a morbid curiosity to know what’s been said and done. Nobody suspected this man in the slightest degree—I, myself, never dreamed of connecting him with this affair. He stayed his night at the Sceptre and went away, crossing these downs. And here!—here he met with this fatal accident, and if he hadn’t, and if we hadn’t found this, and those papers on him, I don’t believe we should ever have known who it was that killed Guy Markenmore! But—we know now.”

He stooped down and drew the dead man’s soft cap more closely over his face. When he looked up again the Professor was still staring thoughtfully at the papers in his hands and Mr. Fransemmery, unusually grave, was watching him. But Harborough was already striding away through the trees, towards Valencia.