Howard Locke stood leaning with his shoulder against one of the verandah pillars. Behind him, in the house, he was conscious of a sort of hushed commotion. Out on the lawn in front of him little groups of negroes stood staring at the house with strained, uplifted faces, or moved across his line of vision in frightened, pathetically humorous efforts to keep an unobtrusive silence—walking on tiptoes in their bare feet on the velvet lawn. Queer how the black faces were mellowed into softer colours in the early morning light!  
Mr. Marlin was dead. Locke's eyes half closed; his lips drew together, compressed in a hard line. Strange! In one sense, he seemed still dazed with the events of the last hour; in another sense, his mind was brutally clear. He was dazed because even yet it seemed impossible to grasp the fact that so sorrowful, and dire, and unrecallable a tragedy was an actual, immutable, existent truth. It was not that Mr. Marlin in a sudden paroxysm of demented frenzy should have done what he had—even to the extent that the old man's attack should have been directed against his, Locke's, person. He could quite understand that. In the aquarium, only a few hours before, the old man had used identically the same words that he had shouted as he had burst in the bedroom door and had begun firing wildly: "You are one of them! ... You are one of them!" And then, apart from what had transpired in the aquarium, there had been the shock of the attack on the path almost immediately afterward. The old man had not lost his money, but he had gone back to the house—he, Locke, had seen that too—and, instead of sleeping, these things had probably preyed and preyed upon his mind until he had lost the little reason that had been left to him and a homicidal mania had developed. All that was quite easily understood. As Polly had said, the specialist had predicted it if the old man became over-excited—and Miss Marlin had feared it. It was not this phase, so logically explainable, of what had happened that affected him still in that dazed, numbed way; it was the fact, so much harder to understand, that quick and sudden, in the passing of a moment, old Mr. Marlin was gone.
 
He straightened up a little, easing the position of his shoulder against the pillar. On the other hand, from an entirely different aspect, that of the consequences as applied to his own course of action, his mind had been clear, irrevocable, settled in its purpose almost from the instant that—first to reach the old madman's side—he had found Mr. Marlin dead. It was the end! He was waiting now for Captain Francis Newcombe to return—from wherever the man had taken himself to.
 
The sight of the awed, grief-stricken figures on the lawn stirred him suddenly with keen emotion. The girls were upstairs in Dora Marlin's room together and— He wrenched his mind away from the course toward which it was trending. For the moment it would do neither them nor himself any good; for the moment he was waiting for—Captain Francis Newcombe.
 
A queer smile came and twisted at his lips. Was it defeat—or victory?
 
The smile passed. His face became grave again. There was Captain Francis Newcombe now—at the far edge of the lawn.
 
The man was strolling leisurely toward the house, then, suddenly pausing for an instant, he as suddenly broke into a run, elbowing his way unceremoniously through the groups of negroes, and, reaching the steps, covered them in a bound to the verandah.
 
"I say!" he burst out breathlessly as he halted before Locke. "Whatever is the matter? This hour in the morning and every light on in the house—and all those negroes out there?"
 
"I've been waiting for you," said Locke quietly. "Come in here." He led the way to the French window by which he had found entry into the house a few hours before, and passed through into the room beyond.
 
Captain Francis Newcombe followed.
 
"I say!" he repeated, closing the glass door with a push behind him. "What's up, old man?"
 
"Mr. Marlin is dead," said Locke briefly.
 
"Dead!" Captain Francis Newcombe stared incredulously. "Why, he wasn't ill—at least not in that way. I don't understand."
 
It was a small room, a sort of adjunct to the library which led off from it toward the rear of the house. Howard Locke's fingers were aimlessly turning the leaves of a book which lay on the table in the centre of the room, and beside which he was standing now.
 
"A belief that he was being followed, that some one was trying to take his money away from him, turned him from a harmless lunatic into a dangerous madman," Locke said slowly. "He seemed to believe that I was, to use his own words, 'one of them,' and he tried to shoot me in my room. The household was aroused. The servants came. We tried to subdue him. But he broke away from us then, and in running down the stairs fell, I think, and his revolver went off in his hand, killing him instantly."
 
"Good God!" said Captain Francis Newcombe heavily. "That's awful! And that poor girl—Miss Marlin!"
 
"Yes," said Howard Locke, his fingers still playing with the leaves of the book.
 
Captain Francis Newcombe appeared to be greatly agitated. He took out his cigarette case, opened and shut it several times, and finally restored it to his pocket with its contents untouched.
 
"It's ghastly!" he ejaculated; and then in a slower, more meditative tone: "But with the shock of it over, I can't say I'm particularly surprised. He struck me as acting in a more than usually peculiar manner all day yesterday, and especially last night, or, rather, this morning—as a matter of fact, it was on account of Mr. Marlin himself that I was out of the house when it happened. He telephoned Polly about four o'clock this morning and nearly frightened her to death. She came to my room in a pitiful state of distress. He told her her mother was dead. God knows why—except that it shows how mad he was. From Polly's description of the conversation during which she had distinctly heard the sound of waves and the slam of a door in the wind, I decided that he must have telephoned from somewhere outside. The only place I could think of was the boathouse. If the man was as bad as that, I was afraid something might happen to him, so I dressed and went out. It is obviously unnecessary to say that I did not find him. Polly and I both decided, on Miss Marlin's account, to say nothing about it, but I can see nothing to be gained now, in view of what has happened, by keeping silent."
 
"No; there could be nothing gained by it now," agreed Locke a little monotonously. "As you imply, it is only cumulative evidence of the man's state of mind just prior to his death."
 
"Exactly!" nodded Captain Francis Newcombe gravely. "But, after all, that is apart from the immediate present. I suppose you have already seen to what you could here in the house, but there still must be many things to do."
 
Howard Locke closed the book, and stepped a little away from the table, a little nearer the other.
 
"There are," he said with quiet deliberation. "But there is one thing in particular for you to do. The mail came over from the mainland very late last night. It naturally hasn't been touched this morning and is still in there"—he motioned toward the door leading from the rear of the room—"on the library table. There is a letter there for you, a very urgent one, demanding your instant return to London."
 
Captain Francis Newcombe's eyes narrowed almost imperceptibly—but his voice was a drawl:
 
"I don't think I quite understand. May I ask how you happen to know the contents of the letter?"
 
"I am speaking in a purely suggestive sense," Locke answered, his voice hardening a little. "There is no letter for you that I know of. I am suggesting a plausible explanation which you can make to Miss Marlin—and Miss Wickes—for leaving this place at once."
 
Captain Francis Newcombe stiffened, but his voice still retained its drawl.
 
"I am tempted to believe that insanity is infectious," he said; "either that, or perhaps my own intelligence is sadly astray this morning. I have neither the desire nor the intention to leave here, and especially at a time such as this when I might possibly be of even a little assistance to those who have been so hospitable to me, and so I do not require any excuse, however plausible or ingenious, for going away."
 
Locke's eyes rested appraisingly for a long moment on the other's cool, composed, suave face. Well, was it any cooler, any more self-possessed than his own? What of passion that was boiling within did not show on the surface!
 
"Nevertheless," he said steadily, "that is the excuse you will give. One of the motor boats is going over to the mainland in a little while, and you are going on her. I have already had your baggage—and Runnells'—put on board."
 
"You—what?" The red was suddenly in Captain Francis Newcombe's face. He took a quick step forward, his hands clenched. "My baggage sent out of the house—by your orders!" he said hoarsely. "You've gone a bit too far now, my man, and you'll explain yourself—and explain yourself damned quick! Out with it! What's the meaning of this?"
 
Locke had not moved. His eyes had not left the other's face. There was something strangely tempting about that face; it induced an almost uncontrollable impulse to mark it, to batter it, to wreck it with a rain of blows that would not cease until physical exhaustion intervened and one could strike no more. And yet his hands hung idly at his sides.
 
"Yes"—Locke's voice was not raised—"I will tell you the meaning of it. You are going for two reasons. The first is because you are morally responsible for Mr. Marlin's death; and the second is because you are—what you are—and as such, from the moment you say good-bye to her here, you are going out of Polly's life forever."
 
Captain Francis Newcombe came still a step nearer.
 
Locke's eyes had not left the other's face. He read a cold, ugly glitter in the gaze that held on his; he saw the curious whitening of the other's lips—and a knotted fist suddenly drawn back to strike. And with a lightning movement Locke caught the other's wrist and flung the blow aside.
 
"Don't do that!" he said in a dead tone. "God knows, it's hard enough to keep my hands off you as it is; but what is between you and me is not measured, or in any way altered by a brawl—and besides I cannot brawl here in this house where Mr. Marlin lies dead, and where there is already distress enough."
 
For a moment Captain Francis Newcombe did not speak; then abruptly he began to laugh, and, stepping over to a chair at the end of the table, flung himself nonchalantly into it.
 
"Upon my soul, Locke," he said coolly, "what I said at first in jest, I believe now must be true. I believe you've gone completely off your head. I'd like to hear why you think I am morally responsible for Mr. Marlin's death; and, particularly, I'd like to know what—"
 
"I want to get this over," said Locke, with a set face. "You are clever. If it appeals to a certain sense of morbid vanity in you, that they say all criminals possess, I grant at once that you are as clever a scoundrel, and as miserable and inhuman and unscrupulous a one, as ever blasphemed the image in which God made him."
 
Captain Francis Newcombe strained upward from the chair, his lips working—but Locke stood over him now and pushed him back.
 
"Don't get up!" he said with savage curtness. "You are going to hear more than that before I am through. I said you were clever—but your cleverness will do you no good here. This is the end, Newcombe. You took a child out of the slums of London—bought her in some unholy fashion, I imagine, from a woman named Mrs. Wickes; you sent the child out of England to America, and educated her in a school, especially selected I also imagine, where she would be brought into intimate contact with, and form her friendships amongst, the daughters of wealthy Americans of high social position. Why? In the light of what has happened, the answer is plain enough: That you might use her introduction into these homes as an entrée for yourself to further your own criminal purposes."
 
Locke paused.
 
A cold sneer had gathered on Captain Francis Newcombe's lips.
 
"You employed the word 'imagine' on both counts," he said. "I congratulate you."
 
"Quite so!" said Locke icily. "I may even employ it again. I am not imagining, however, when I say that you received a letter from Polly telling you that Mr. Marlin had half a million dollars in cash here on this island, and—"
 
"Did Polly tell you that?" demanded Captain Francis Newcombe sharply.
 
"Innocently—yes," Locke answered. "And in her letter she also told you 'all about everything here,' to use her own words, which could not help but embrace the fact that Mr. Marlin was not right in his mind—yet, strangely enough, in the smoking room of the liner, you will perhaps remember, you had had no idea of any such thing, and even expressed anxiety for the safety of your ward."
 
Captain Francis Newcombe was painstakingly polishing the finger nails of one hand on the palm of the other now.
 
"One might possibly conceive a man to be eccentric and attribute his idiosyncrasies to that cause—without thought of classifying him as a raving lunatic," he observed in a bored voice.
 
Locke shrugged his shoulders.
 
"Perhaps there is a better explanation of your mistake," he said evenly. "You did not, at that time, have the slightest idea that I, too, would be one of the party on this island."
 
Captain Francis Newcombe looked up from his finger nails.
 
"Did you?" he inquired softly.
 
"Yes," said Locke curtly.
 
"Ah!" Captain Francis Newcombe, with eyes half closed now, studied Locke's face for a full minute before he spoke again. "I am becoming rather curious as to just who you are, Locke," he murmured finally.
 
"You ought to know," Locke responded grimly. "I imagine it was you who went through my papers that night in my cabin."
 
"That is the third time," suggested Captain Francis Newcombe, "that you have said 'imagine.'"
 
"Yes." Locke smiled without humour. "I happen to know, however, that from the moment of your arrival here Mr. Marlin became more and more obsessed with the belief that he was being watched and followed. I know from his own statement that he rather cunningly laid a false trail—to an old hut in the woods behind the house, wasn't it, Newcombe? And it is rather conclusive evidence, I should say, that the man who followed that trail was the man who was watching Mr. Marlin. I saw you coming from that direction at three o'clock this morning. You were unsuccessful, of course; but you are none the less, as I said before, morally responsible for Mr. Marlin's death."
 
Captain Francis Newcombe leaned back in his chair, and laughed softly, insolently, contemptuously.
 
"As I understand the indictment," he said coolly, "it is to the effect that I left London for the purpose of coming here and stealing some money that I knew a madman had hidden. The evidence against me is from beginning to end purely circumstantial, and most of it is admittedly imaginative. The one 'damning' fact adduced is that I was seen coming from somewhere at three o'clock this morning. This is a bit thick, Locke—coming from you!" His voice was beginning to lose its suavity. "You don't imagine, do you, that any such 'case' as that would hold water for an instant in any court of law?"
 
"No," said Locke quietly; "I know it wouldn't. I quite agree with you there."
 
Captain Francis Newcombe's face for an instant held a look of puzzlement, as though he had not heard aright—then it stiffened into ugly menace.
 
"I think you need a lesson!" He spoke from between set lips. "This is no longer merely ridiculous, or absurd, or cracked-brained. It is monstrous!"
 
"Again I agree with you." Locke's voice was low now, rasping his words. "It is so monstrous that, strong as the circumstantial evidence against you is, I would not have been able to credit it had I not had a basis for belief that permitted of no denial. I know you for exactly what you are. I know that you are a criminal, that you are one by profession, that you have no other profession, that you are without conscience, inhuman, ruthless, a fiend who would do honour to hell itself."
 
"By God!" Captain Francis Newcombe with livid face surged up from the chair to his feet.
 
But Locke's face, too, was white now with passion, as with a suddenly outflung hand he thrust the other away.
 
"I am not through yet," he said. "Denial, any attitude of pretended righteous indignation, or any other attitude that may suggest itself to you as the best mask to adopt, is hardly worth your while when attempted with one who once very narrowly escaped being one of your victims—with a man who once, because you feared he possessed the information that you know now he does possess, you tried to murder w............