Nick actually had his mouth open to call to his wide-awake second assistant, when a crash that might have meant the blowing up of the whole building stopped him. The sound began with a swish such as often precedes the boom of an explosion of certain kinds of chemicals. It was followed immediately by a heaven-splitting cr-r-rack, and then by the thunderous letting go of what might have been one of the heaviest guns known to modern ordnance. Simultaneously, the big wooden warehouse rocked on its foundations, and Chick fell from the window ledge back to the cellar. Down went Nick to the floor after him. He had only just got there, and placed his hands on the clothing of his assistant, when another explosion, even more terrifying than the first, sent the stone-wall foundations scattering in all directions. Nick found himself hemmed in by heaps of splintered wood, while the upper part of the building, caving in one side, formed an arch over him that threatened to collapse at any moment. “Chick!” he cried. “Where are you?” There was no answer. He had not expected any. His assistant had slipped from his grasp at the second explosion, and the general disturbance had separated them. In the heaps of débris it was impossible for Nick to see him at once. “Heaven preserve us!” muttered the detective. “I’ve _got_ to find him!” Outside the building he could hear Patsy shouting to him, while the oaths of the prisoners, as they commanded Patsy to get the boat farther away from the destroyed warehouse, told plainly enough that his second assistant had special troubles of his own. “Patsy!” cried Nick, at the top of his voice. “Stay where you are! I’ll bring Chick!” He did not know whether his voice had carried to Patsy or not. Indeed, he had no time to think about it, for suddenly, with a vicious roar, a blue-and-yellow tongue of flame shot up from the middle of the great heaps of timbers about him, and through the caved-in roof overhead. The warehouse was on fire! CHAPTER XII. ROUNDED UP. “Chick!” shouted Nick Carter, in agony. “Where are you?” Again there was no answer. Nick Carter would have been surprised if there had been. Well he knew that if Chick was to be rescued, it must be without any help from the imperiled one himself. Fragments of blazing timbers were beginning to fall, and Nick saw that if certain joists already on fire should burn through, down would come the tons of flooring and roof upon his head. Nothing could save him. If he meant to get Chick out of this, he must do it quickly. “There he is--on the other side of that heap of burning wood,” he muttered. “Merciful heavens! Some of it is resting on him. He may be slowly roasting to death! I must get to him!” It was a perilous trip the detective had now. Mounds of rubbish had been built up by the explosions, and had caught fire afterward. Nick had to climb over them.