There might be a trap in store, but Nick, in view of the importance of the pursuit, determined to risk the danger. He came to the opening just as Slack was entering the door of a wooden lean-to of one of the brick buildings. From his observation of the locality taken while passing the block many times, either on his way to the depot or the court buildings, Nick was satisfied that his quarry had gone into an unoccupied section of the block. The rooms, sandwiched between a cheap hotel and a ticket-scalper's office, had been the headquarters of a band of fakers, whose operations, not coming within the limits of the law, had been summarily discountenanced by the police. There was the possibility, which, on account of the former deputy jailer's good record, had in it strong elements of reason, that Slack was really trying to evade Nick Carter, and that he hoped by darting through the vacant rooms to slip through to Market Street, and on into one of the near-by hotels or saloons, where backway exit to safety might be found. Nick opened the door of the lean-to, and entered what had been intended for a kitchen. Probably the rooms had last been put to legitimate use by a restaurateur. There was no one in the room, and Nick, without a moment's pause, hurried toward another, the middle room beyond, the door of which was partly open. At the threshold he stopped and struck the door a resounding blow, which caused it to fly backward against the wall. Nothing of a suspicious nature met his gaze. The room, as far as he could see, was bare. While walking slowly in, so as to guard against possible surprise from some unexpected quarter, a heavy body struck him on the shoulders and back, and he was borne violently to the floor. Over the door was a wide shelf, and from that shelf a man had leaped. The suddenness, as well as the force of the assault, caught Nick without that tension of mind and muscle which is of such efficacy at critical times. For a moment he lay flat upon his stomach, the while his adversary was reaching to grasp his windpipe. Then, with a mighty effort, Nick Carter called all his wonderful strength into play. With one hand planted on the floor, he turned sidewise, made a sudden twist, and flung Slack off. But the former deputy jailer was as quick in movements as a cat, and he rolled over and clutched Nick about the waist before the detective could make an offensive move. The two instantly became locked in a deadly embrace. Nick was the more powerful and scientific, but Slack was a strong man, and he fought as if for his life. He soon gained an advantage, but it was not lasting. Nick, upon Slack's initial onslaught, had sprained his ankle, and the San Franciscan, in exerting all his energies to bring the detective's back to the floor, unintentionally pressed his legs against the injured member, twisting it so that Nick, in the intensity of his pain, slightly relaxed his hold, and was rolled over in consequence.