"Any particular object in that course?" David asked.

"There ought to be an object in everything that even an irrational man says or does," Bell replied. "I have achieved some marvellous results by following up a single sentence uttered by a patient. Besides, on the evening in question you were particularly told to approach the house from the sea front."

"Somebody might have been on the look-out near the Western Road entrance," Steel suggested.

"Possibly. I have another theory…. Here we are. The figures over the fanlights run from 187 upwards, gradually getting to 219 as you breast the slope. At one o'clock in the morning every house would be in darkness. Did you find that to be so?"

"I didn't notice a light anywhere till I reached 219."

"Good again. And you could only find 219 by the light over the door. Naturally you were not interested in and would not have noticed any other number. Well, here is 218, where I propose to enter, and for which purpose I have the keys. Come along."

David followed wonderingly. The houses in Brunswick Square are somewhat irregular in point of architecture, and Nos. 218 and 219 were the only matched pair thereabouts. Signs were not wanting, as Bell pointed out, that at one time the houses had been occupied as one residence. The two entrance-halls were back to back, so to speak, and what had obviously been a doorway leading from one to the other had been plastered up within comparatively recent memory.

The grim and dusty desolation of an empty house seemed to be supplemented here by a deeper desolation. Not that there was any dust on the ground floor, which seemed a singular thing seeing that elsewhere the boards were powdered with it, and festoons of brown cobwebs hung everywhere. Bell smiled approvingly as David Steel pointed the fact out to him.

"Do you note another singular point?" the former asked.

"No," David said, thoughtfully; "I—stop! The two side-shutters in the bay-windows are closed, and there is the same vivid crimson blind in the centre window. And the self colour of the walls is exactly the same. The faint discoloration by the fireplace is a perfect facsimile."

"In fact, this is the room you were in the other night," Bell said, quietly.

"Impossible!" Steel cried. "The blind may be an accident, so might the fading of the distemper. But the furniture, the engravings, the fittings generally—"

"Are all capable of an explanation, which we shall arrive at with patience."

"Can we arrive at the number over the door with patience?"

"Exactly what I was coming to. I noticed an old pair of steps in the back sitting-room. Would you mind placing them against the fanlight for me?"

David complied readily enough. He was growing credulous and interested in spite of himself. At Bell's instigation he placed the steps before the fanlight and mounted them. Over his head were the figures 218 in elongated shape and formed in white porcelain.

"Now then," Bell said, slowly. "Take this pocket-knife, apply the blade to the right-hand lower half of the bottom of the 8—to half the small O, in fact—and I shall be extremely surprised if the quarter section doesn't come away from the glass of the fanlight, leaving the rest of the figure intact. Very gently, please. I want you to convince yourself that the piece comes away because it is broken, and not because the pressure has cracked it. Now then."

The point of the knife was hardly under the edge of the porcelain before the segment of the lower circle dropped into Steel's hand. He could feel the edges of the cement sticking to his fingers. As yet the full force of the discovery was not apparent to him.

"Go out into the road and look at the fanlight," Bell directed.

David complied eagerly. A sharp cry of surprise escaped him as he looked up. The change was apparent. Instead of the figures 218 he could read now the change to 219—a fairly indifferent 9, but one that would have passed muster without criticism by ninety-nine people out of a hundred. With a strong light behind the figures the clumsy 9 would never have been noticed at all. The very simplicity and ingeniousness of the scheme was its safeguard.

"I should like to have the address of the man who thought that out,"
David said, drily.

"Yes, I fancy that you are dealing with quite clever people," Bell replied. "And now I have shown you how utterly you have been deceived over the number we will go a little farther. For the present, the way in which the furniture trick was worked must remain a mystery. But there has been furniture here, or this room and the hall would not have been so carefully swept and garnished whilst the rest of the house remains in so dirty a condition. If my eyes don't deceive me I can see two fresh nails driven into the archway leading to the back hall. On those nails hung the curtain that prevented you seeing more than was necessary. Are you still incredulous as to the house where you had your remarkable adventure?"

"I confess that my faith has been seriously shaken," David admitted. "But about the furniture? And about my telephone call from Mr. Gates's town house? And about my adventure taking place in the very next house to the one taken by him at Brighton? And about Miss Gates's agitation when she learnt my identity? Do you call them coincidences?"

"No, I don't," Bell said, promptly. "They are merely evidences of clever folks taking advantage of an excellent strategic position. I said just now that it was an important point that Mr. Gates had merely taken the next door furnished. But we shall come to that side of the theory in due course. Have you any other objection to urge?"

"One more, and I have finished for the present. When I came here the other night—provided of course that I did come here—immediately upon my entering the dining-room the place was brilliantly illuminated. Now, directly the place was void the supply of electric current would be cut off at the meter. So far as I can judge, some two or three units must have been consumed during my visit. There could not be many less than ten lights burning for an hour. Now, those units must show on the meter. Can you read an electric meter?"

"My dear fellow, there is nothing easier."

"Then let us go down into the basement and settle the matter. There is pretty sure to be a card on the meter made up to the day when the last tenant went out. See, the supply is cut off now."

As Steel spoke he snapped down the hall switch and no result came. Down in the basement by the area door stood the meter. Both switches were turned off, but on Bell pressing them down Steel was enabled to light the passage.

"There's the card," Bell exclaimed. "Made up to 25th June, 1895, since when the house has been void. Just a minute whilst I read the meter. Yes, that's right. According to this the card in your hand, provided that the light has not been used since the index was taken, should read at 1521. What do you make of the card?"

"1532," David cried. "Which means eleven units since the meter was last taken. Or, if you like to put it from your point of view, eleven units used the night that I came here. You are quite right, Bell. You have practically convinced me that I have been inside the real 219 for the first time to-day. And yet the more one probes the mystery the more astounding does it become…. What do you propose to do next?"

"Find out the name of the last tenant or owner." Bell suggested. "Discover what the two houses were used for when they were occupied by one person. Also ascertain why on earth the owners are willing to let a house this size and in this situation for a sum like £80 per annum. Let us go and take the keys back to the agents."

Steel was nothing loth to find himself in the fresh air again. Some progress had been made like the opening of a chess-match between masters, and yet the more Steel thought of it the more muddled and bewildered did he become. No complicated tangle in the way of a plot had ever been anything like the skein this was.

"I'm like a child in your hands," he said. "I'm a blind man on the end of a string; a man dazed with wine in a labyrinth. And if ever I help a woman again—"

He paused as he caught sight of Ruth Gates's lovely face through the window of No. 219. Her features were tinged with melancholy; there was a look of deepest sympathy and feeling and compassion in her glorious eyes. She slipped back as Steel bowed, and the rest of his speech was lost in a sigh.