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.