“You’ll have to explain that,” said the police chief, who seemed out of his depth.
“I mean that we are now in the original White House. I led you back here, didn’t I? And I can lead you back to the twin White House, for now I know the basis of the illusion. After our departure this evening, incidentally, all these people returned to this house. The other White House had served its purpose and they no longer needed it.
“As for the geographical trick involved, it struck me that this side-road we’re on makes a steady curve for miles. Both driveways lead off this same road, one some six miles farther up the road; although, because of the curve, which is like a number 9, the road makes a wide sweep and virtually doubles back on itself, so that as the crow flies the two settlements are only a mile or so apart, although by the curving road they are six miles apart.
“When Dr. Reinach drove Thorne and Miss Mayhew and me out here the day the Coronia docked, he deliberately passed the almost imperceptible drive leading to the substitute house and went on until he reached this one, the original. We didn’t notice the first driveway.
“Thome’s car was put out of commission deliberately to prevent his driving. The driver of a car will observe landmarks when his passengers notice little or nothing. Keith even met Thorne on both Thome’s previous visits to Mayhew — ostensibly ‘to lead the way,’ actually to prevent Thorne from familiarizing himself with the road. And it was Dr. Reinach who drove the three of us here that first day. They permitted me to drive away tonight for what they hoped was a one-way trip because we started from the substitute house — of the two, the one on the road nearer to town. We couldn’t possibly, then, pass the tell-tale second drive and become suspicious. And they knew the relatively shorter drive would not impress our consciousness.”
“But even granting all that, Mr. Queen,” said the policeman, “I don’t see what these people expected to accomplish. They couldn’t hope to keep you folks fooled forever.”
“True,” cried Ellery, “but don’t forget that by the time we caught on to the various tricks involved they hoped to have laid hands on Mayhew’s fortune and disappeared with it. Don’t you see that the whole illusion was planned to give them time? Time to dismantle the Black House without interference, raze it to the ground if necessary, to find that hidden hoard of gold? I don’t doubt that if you examine the house next door you’ll find it a shambles and a hollow shell. That’s why Reinach and Keith kept disappearing. They were taking turns at the Black House, picking it apart, stone by stone, in a frantic search for the cache, while we were occupied in the duplicate White House with an apparently supernatural phenomenon. That’s why someone — probably the worthy doctor here — slipped out of the house behind your back, Thorne, and struck me over the head when I rashly attempted to follow Keith’s tracks in the snow. I could not be permitted to reach the original settlement, for if I did the whole preposterous illusion would be revealed.”
“How about that gold?” growled Thorne.
“For all I know,” said Ellery with a shrug, “they’ve found it and salted it away again.”
“Oh, but we didn’t,” whimpered Mrs. Reinach, squirming in her chair. “Herbert, I told you not to—”