Just now he gave the one before which he stood no thought at all, his mind being occupied by his unfortunate situation, and his immediate attention attracted by the bat-like cry from above.
His surprise was, therefore, intense when he suddenly perceived the iron door softly open to an extent sufficient to admit the body of a man.
In the aperture stood a boyish form, rendered plainly visible by the light of a street lamp which stood directly opposite the door itself.
Nor was his surprise less in recognizing in the face before him that of a bootblack who had every afternoon for more than a year past polished his shoes at the close of business hours at the bank.
With a quick movement the boy extended his hand and silently beckoned to him to come in.
The policeman was still skirmishing along the foot of the wall with his head in the air, for that the whole thing occupied but the space of an instant must be distinctly understood, and yielding to an uncontrollable impulse, without the slightest thought of what the result of such action might be, Frank stepped within the iron door by the bootblack's side.
In an instant the door was noiselessly closed behind him, rendering the darkness entire.
The boy, without a word, took Frank by the arm and led him forward, up several steps, and opening a second door of iron like the first, ushered him into a low-vaulted apartment not higher than his head.
"There you are, Mr. Mansfield," said the boy, respectfully. "I tought I could do it, an' I have. I'd like to see the cop as could catch onto yer now!"
"Why, you're Barney, the bootblack, ain't you?" demanded Frank, glancing about him in curious surprise.