Presently, as though from a great distance, the cry was repeated. Whether from above or below no one could have told. Indeed, it seemed as much as anywhere to come from out of the wall itself. Frank remained silently waiting. Presently the great iron door swung slowly back, and a boy's head appeared in the opening. "Is that you, Frank Mansfield?" "Yes. Is that you, Jerry Buck?" "Slide in, young feller," said the boy, in a whisper. "I'm a-scart to hold the door open long. After all that happened last night I'm expecting every minute that some one will catch onto our hole in the wall." His sentence was completed within the old tomb itself, for Frank had entered at the first word, the door being closed behind him and securely barred. "Come up to the den," said Jerry, leading the way up the steps. "Most of the fellers is in to-night and are abed long ago. I know'd you'd keep your promise and come, so me and Barney sat up to let you in." Entering the inner apartment of the tomb, Frank found that the boy had spoken the truth. Barney the boot-black sat smoking a clay pipe by the side of the table, upon which was a loaf of bread and a mug. "Hello! I know'd you'd come!" said the bootblack, springing up. "Have you had your supper? I kept some in case you didn't." "Thank you. I've had all I want," replied Frank, sinking wearily upon an old stool. "I'm tremendously obliged to you fellows for your kindness to me. Mebbe I shall be able to return it some of these days." "That's all right," put in Jerry Buck. "If I can help any friend of Barney's, I'm glad to do it." "Hush!" cried Barney, holding up his finger warningly as Frank was about to reply. "Jerry, as true as I live there's some one up above. I didn't hear no signal, did you?" The three boys stood motionless. Above their heads, at the top of the ladder, down which Frank had seen the two boys descend upon the occasion of his first visit to the tomb, a grating sound was heard--such a sound as might be made by the rising of a tightly-fitting trap-door. At the same instant two feet were seen upon the top round of the ladder, which, descending, were followed by the legs and body of a man. "Twigged at last, by thunder!" exclaimed Jerry Buck, uttering a warning cry, which had the effect of instantly arousing several sleeping boyish forms stretched upon pieces of old carpet at various angles upon the floor. At the same instant a man sprang from the ladder and stood in their midst. "Good-evening, boys," he said, quietly. "So this is where you hang out? Upon my word, now, it ain't half a bad place. I've slept in many a worse one myself." CHAPTER XV. CALEB HOOK MAKES HIMSELF AT HOME. The boys stared at the man who had leaped among them from off the ladder with feelings of alarmed surprise. Nor was the surprise of Frank Mansfield less than the others. It was Detective Hook who stood before him--Detective Hook, whom he had supposed to be already far upon his homeward way.