Ellery went to her and put his hand on her shoulder. “Alice Mayhew vanished and you took her place. Why did you take her place? For two possible reasons. One — to get Thorne and me away from the danger zone as quickly as possible, and to keep us away by ‘abandoning’ the fortune or dismissing us, which as Alice Mayhew would be your privilege: in proof, your vociferous insistence that we take you away. Two — of infinitely greater importance to the scheme: if your confederates did not find the gold at once, you were still Alice Mayhew in our eyes. You could then dispose of the house when and as you saw fit. Whenever the gold was found, it would be yours and your accomplices’. “But the real Alice Mayhew vanished. For you, her impersonator, to be in a position to go through the long process of taking over Alice Mayhew’s inheritance, it was necessary that Alice Mayhew remain permanently inirisible. For you to get possession of her rightful inheritance and live to enjoy its fruits, it was necessary that Alice Mayhew die. And that, Thorne,” snapped Ellery, gripping the girl’s shoulder hard, “is why I said that there was something besides a disappearing house to cope with tonight. Alice Mayhew was murdered.”
There were three shouts from outside which rang with tones of great excitement. And then they ceased, abruptly.
“Murdered,” went on Ellery, “by the only occupant of the house who was not in the house when this impostor came downstairs that first evening — Nicholas Keith. A hired killer. Although these people are all accessories to that murder.”
A voice said from the window: “Not a hired killer.”
They wheeled sharply, and fell silent. The three detectives who had sprung out of the window were there in the background, quietly watchful. Before them were two people.
“Not a killer,” said one of them, a woman. “That’s what he was supposed to be. Instead, and without their knowledge, he saved my life... dear Nick.”
And now the pall of grayness settled over the faces of Mrs. Fell, and of Olivia Fell, and of Mrs. Reinach, and of the burly doctor. For by Keith’s side stood Alice Mayhew. She was the same woman who sat near the fire only in general similitude of feature. Now that both women could be compared in proximity, there were obvious points of difference. She looked worn and grim, but happy withal; and she was holding to the arm of bitter-mouthed Nick Keith with a grip that was quite possessive.
Addendum
Afterwards, when it was possible to look back on the whole amazing fabric of plot and event, Mr. Ellery Queen said: “The scheme would have been utterly impossible except for two things: the character of Olivia Fell and the — in itself — fantastic existence of that duplicate house in the woods.”
He might have added that both of these would in turn have been impossible except for the aberrant strain in the Mayhew blood. The father of Sylvester Mayhew — Dr. Reinach’s stepfather — had always been erratic, and he had communicated his unbalance to his children. Sylvester and Sarah, who became Mrs. Fell, were twins, and they had always been insanely jealous of each other’s prerogatives. When they married in the same month, their father avoided trouble by presenting each of them with a specially-built house, the houses being identical in every detail. One he had erected next to his own house and presented to Mrs. Fell as a wedding gift; the other he built on a piece of property he owned some miles away and gave to Sylvester.