To my surprise the house was boarded up. Nearly every window was boarded, even the top-floor windows. It looked like a house in which people have died of some plague. I found the policeman on the beat, and questioned him. Inclined at first to be sullen and uncommunicative, he became cordial and confidential soon after my fingers had slipped a coin into his hand. "So you haven't heard anything about number a hundred and two," he said some moments later. "About here it's causin' a bit o' talk." "Indeed? In what way?" He paused, as though reflecting whether he ought to tell me. "Well, sir, it's like this," he said at last. "The 'ouse is, as you've seen, boarded up, and there's nobody living there but--" "Yes? But what?" "Well, for the last eight nights there's been a light in a window on the first floor." "A light? But how could you see a light if there were one, with the windows boarded up?" "Oh, it can be seen right enough, through the chinks between the boards." "Who has seen it?" "I have--and others also." "Is it always in the same window?" "Not always in the same window, but always on the same floor. Ah, no! On two nights there was a light on the second floor too." "And at what time is it seen?" "Very late--not before two in the morning, as a rule." "And how long does it remain?" "Sometimes for five or ten minutes, sometimes as much as half-an-hour, or more. Three nights ago two windows were lit up at one-twenty and remained lit until two-fifty-five." "And do you mean to say nobody goes into the house or comes out of it?" "Nobody. Nobody at all. It's being watched front and back. Twice we've been in and hunted the place all over--we got leave to do this-- but there was nothing, nor no one nowhere." "Oh," I exclaimed incredulously, "that is a ridiculous thing to say. If a light really appears and disappears, there must be somebody in the house. Probably there's a secret entrance of which you know nothing about." "There are only three entrances," he answered quickly, "and one of 'em can't rightly be called an entrance. There's the front door, and the back door for the tradesmen, and then there's a queer little way out into Crane's alley--we can't think why that entrance was ever made." The "queer little way out" I at once guessed to be the dark, underground, narrow little stone cellar-passage through which Vera had led me when we had escaped together on the day I had discovered her hidden in the house. "And are the entrances all locked?" I asked. "Oh, you may take that from me," he replied. "They are locked right enough, and nobody don't get the keys, neither." At that moment, oddly enough, the thought of the curious-looking brown stain in the corner of the ceiling on the first floor, that I had noticed on the day I had explored the unoccupied house, came suddenly back into my mind.