that he would willingly spend the time just to watch such an unheard-of instrument work. After another hour of fruitless discussion Prescott took his leave, saying that he would mount an impregnable guard from that time on.
Late that evening Prescott joined the two men who were watching DuQuesne's house. They reported that all was perfectly quiet, as usual. The scientist was in his library, the instruments registering only the usual occasional faint sounds of a man absorbed in study. But after an hour of waiting, and while the microphones made a noise as of rustling papers, the needle of the compass moved. It dipped slowly toward the earth as though DuQuesne were descending into the cellar, but at the same time the shadow of his unmistakable profile was thrown upon the window shade as he apparently crossed the room.
"Can't you hear him walk?" demanded Prescott.
"No. He has heavy Turkish rugs all over the library, and he always walks very lightly, besides."
Prescott watched the needle in amazement as it dipped deeper and deeper, pointing down into the earth almost under his feet and then behind him, as though DuQuesne had walked beneath him. He did not, could not, believe it. He was certain that something had gone wrong with the strange instrument in his hand, nevertheless he followed the pointing needle. It led him beside Park Road, down the hill, straight toward the long bridge which forms one entrance to Rock Creek Park. Though skeptical, Prescott took no chances, and as he approached the bridge he left the road and concealed himself behind a clump of trees, from which point of vantage he could see the ground beneath the bridge as well as the roadway. Soon the bridge trembled under the weight of a heavy automobile going toward the city at a high rate of speed. He saw DuQuesne, with a roll of papers under his arm, emerge from under the bridge just in time to leap aboard the automobile, which slowed down only enough to enable him to board it in safety. The detective noticed that the car was a Pierce-Arrow limousine—a car not common, even in Washington—and rushed out to get its number, but the license plates were so smeared with oil and dust that the numbers could not be read by the light of the tail lamp. Glancing at the compass in his hand he saw that the delicate needle was now pointing steadily at the fleeing car, and all doubts as to the power of the instrument were dispelled. He rejoined his men, informed them that DuQuesne had eluded them, and took one of them up the hill to a nearby garage. There he engaged a fast car and set out in pursuit, choosing the path for the chauffeur by means of the compass. His search ended at the residence of Brookings, the General Manager of the great World Steel Corporation. Here he dismissed the car and watched the house while his assistant went to bring out the fast motorcycle used by Prescott when high speed was desirable.
After four hours a small car bearing the license number of a distant state—which was found, by subsequent telegraphing, to be unknown to the authorities of that state—drove under the porte-cochère, and the hidden watcher saw DuQuesne, without the papers, step into it. Knowing now what to expect, Prescott drove his racing motorcycle at full speed out to the Park Road Bridge and concealed himself beneath the structure, in a position commanding a view of the concrete abutment through which the scientist must have come. Soon he heard a car slow down overhead, heard a few rapid footfalls, and saw the dark form of a large man outlined against the gray face of the abutment. He saw the man lift his hand high above his head, and saw a black rectangle appear in the gray, engulf the man, and disappear. After a few minutes he approached the abutment and searched its face with the help of his flash-light. He finally succeeded in tracing the almost imperceptible crack which outlined the door, and the concealed button which DuQuesne had pressed to open it. He did not press the button, as it might be connected to an alarm. Deep in thought, he mounted his motorcycle and made his way to his home to get a few hours of sleep before reporting to Crane whom he was scheduled to see at breakfast next morning.
Both men were waiting for him when he appeared, and he noticed with pleasure that Shiro, with a heavily-bandaged head, was insisting that he was perfectly able to wait on the table instead of breakfasting in bed. He calmly proceeded to serve breakfast in spite of Crane's remonstrances, having ceremoniously ordered out of the kitchen the colored man who had been secured to take his place.
"Well, gentlemen," the detective began, "part of the mystery is straightened out. I was entirely wrong, and each of you were partly right. It was DuQuesne, in all probability. It is equally probable that a great company—in this case the World Steel Corporation—is backing him, though I don't believe there is a ghost of a show of ever being able to prove it in law. Your 'object-compass' did the trick."
He narrated all the events of the previous night.
"I'd like to send him to the chair for this job," said Seaton with rising anger. "We ought to shoot him anyway, damn him—I'm sorry duels have gone out of fashion, for I can't shoot him off-hand, the way things are now—I sure wish I could."
"No, you cannot shoot him," said Crane, thoughtfully, "and neither can I, worse luck. We are not in his class there. And you must not fight with him, either"—noting that Seaton's powerful hands had doubled into fists, the knuckles showing white through the tanned skin—"though that would be a fight worth watching and I would like to see you give him the beating of his life. A little thing like a beating is not a fraction of what he deserves and it would show him that we have found him out. No, we must do it legally or let him entirely alone. You think there is no hope of proving it, Prescott?"
"Frankly, I see very little chance of it. There is always hope, of course, and if that bunch of pirates ever makes a slip, we'll be right there waiting to catch 'em. While I don't believe in holding out false encouragement, they've never slipped yet. I'll take my men off DuQuesne, now that we've linked him up with Steel. It doesn't make any difference, does it, whether he goes to them every night or only once a week?
"No."
"Then about all I can do is to get everything I can on that Steel crowd, and that is very much like trying to get blood out of a turnip. I intend to keep after them, of course, for I owe them something for killing two of my men here, as well as for other favors they have done me in the past, but don't expect too much. I have tackled them before, and so have police headquarters and even the Secret Service itself, under cover, and all that any of us has been able to get is an occasional small fish. We could never land the big fellows. In fact, we have never found the slightest material proof of what we are morally certain is the truth, that World Steel is back of a lot of deviltry all over the country. The little fellows who do the work either don't know anything or are afraid to tell. I'll see if I can find out what they are doing with the stuff they stole, but I'm not even sure of doing that. You can't plant instruments on that bunch—it would be like trying to stick a pin into a sleeping cat without waking him up. They undoubtedly have one of the best corps of detectives in the world. You haven't perfected an instrument which enables you to see into a closed room and hear what is going on there, have you?" And upon being assured that they had not, he took his leave.
"Optimistic cuss, ain't he?" remarked Seaton.
"He has cause to be, Dick. World Steel is a soulless corporation if there ever was one. They have the shrewdest lawyers in the country, and they get away legally with things that are flagrantly illegal, such as freezing out competitors, stealing patents, and the like. Report has it that they do not stop at arson, treason, or murder to attain their ends, but as Prescott said, they never leave any legal proof behind them."
"Well, we should fret, anyway. Of course, a monopoly is what they're after, but they can't form one because they can't possibly get the rest of our solution. Even if they should get it, we can get more. It won't be as easy as this last batch was, since the X was undoubtedly present in some particular lot of platinum in extraordinary quantities, but now that I know exactly what to look for, I can find more. So they can't get their monopoly unless they kill us off...."
"Exactly. Go on, I see you are getting the idea. If we should both conveniently die, they could get the solution from the company, and have the monopoly, since no one else can
