Other boxes addressed to O. Brotherson had been received at the station, and carried to the mysterious shed in the woods; and now, with locked door and lifted top, the elder brother contemplated his stores and prepared himself for work.

He had been allowed a short interview with Oswald, and he had indulged himself in a few words with Doris. But he had left those memories behind with other and more serious matters. Nothing that could unnerve his hand or weaken his insight should enter this spot sacred to his great hope. Here genius reigned. Here he was himself wholly and without flaw;—a Titan with his grasp on a mechanical idea by means of which he would soon rule the world.

Not so happy were the other characters in this drama. Oswald’s thoughts, disturbed for a short time by the somewhat constrained interview he had held with his brother, had flown eastward again, in silent love and longing; while Doris, with a double dread now in her heart, went about her daily tasks, praying for strength to endure the horrors of this week, without betraying the anxieties secretly devouring her. And she was only seventeen and quite alone in her trouble. She must bear it all unassisted and smile, which she did with heavenly sweetness, when the magic threshold was passed and she stood in her invalid’s presence, overshadowed though it ever was by the great Dread.

And Mr. Challoner? Let those endless walks of his through the woods and over the hills tell his story if they can; or his rapidly whitening hair, and lagging step. He had been a strong man before his trouble, and had the stroke which laid him low been limited to one quick, sharp blow he might have risen above it after a while and been ready to encounter life again. But this long drawn out misery was proving too much for him. The sight of Brotherson, though they never really met, acted like acid upon a wound, and it was not till six days had passed and the dreaded Sunday was at hand, that he slept with any sense of rest or went his way about the town without that halting at the corners which betrayed his perpetual apprehension of a most undesirable encounter.

The reason for this change will be apparent in the short conversation he held with a man he had come upon one evening in the small park just beyond the workmen’s dwellings.

“You see I am here,” was the stranger’s low greeting.

“Thank God,” was Mr. Challoner’s reply. “I could not have faced to-morrow alone and I doubt if Miss Scott could have found the requisite courage. Does she know that you are here?”

“I stopped at her door.”

“Was that safe?”

“I think so. Mr. Brotherson—the Brooklyn one,—is up in his shed. He sleeps there now, I am told, and soundly too I’ve no doubt.”

“What is he making?”

“What half the inventors on both sides of the water are engaged upon just now. A monoplane, or a biplane, or some machine for carrying men through the air. I know, for I helped him with it. But you’ll find that if he succeeds in this undertaking, and I believe he will, nothing short of fame awaits him. His invention has startling points. But I’m not going to give them away. I’ll be true enough to him for that. As an inventor he has my sympathy; but—Well, we will see what we shall see, to-morrow. You say that he is bound to be present when Miss Scott relates her tragic story. He won’t be the only unseen listener. I’ve made my own arrangements with Miss Scott. If he feels the need of watching her and his brother Oswald, I feel the need of watching him.”

“You take a burden of intolerable weight from my shoulders. Now I shall feel easier about that interview. But I should like to ask you this: Do you feel justified in this continued surveillance of a man who has so frequently, and with such evident sincerity, declared his innocence?”

“I do that. If he’s as guiltless as he says he is, my watchfulness won’t hurt him. If he’s not, then, Mr. Challoner, I’ve but one duty; to match his strength with my patience. That man is the one great mystery of the day, and mysteries call for solution. At least, that’s the way a detective looks at it.”

“May Heaven help your efforts!”

“I shall need its assistance,” was the dry rejoinder. Sweetwater was by no means blind to the difficulties awaiting him.