Mrs. Fell’s husband died early in her married life; and she moved away to live with her half-brother Herbert. When old Mayhew died, Sylvester boarded up his own house and moved into the ancestral mansion. And there the twin houses stood for many years, separated by only a few miles by road, completely and identically furnished inside — fantastic monuments to the Mayhew eccentricity.
The duplicate White House lay boarded up, waiting, idle, requiring only the evil genius of an Olivia Fell to be put to use. Olivia was beautiful, intelligent, accomplished, and as unscrupulous as Lady Macbeth. It was she who had influenced the others to move back to the abandoned house next to the Black House for the sole purpose of coercing or robbing Sylvester Mayhew. When Thorne appeared with the news of Sylvester’s long-lost daughter, she recognized the peril to their scheme and, grasping her own resemblance to her English cousin from the photographs Thorne brought, conceived the whole extraordinary plot.
Then obviously the first step was to put Sylvester out of the way. With perfect logic, she bent Dr. Reinach to her will and caused him to murder his patient before the arrival of Sylvester’s daughter. (A later exhumation and autopsy revealed traces of poison in the corpse.) Meanwhile, Olivia perfected the plans of the impersonation and illusion.
The house illusion was planned for the benefit of Thorne, to keep him sequestered and bewildered while the Black House was being torn down in the search for the gold. The illusion would perhaps not have been necessary had Olivia felt certain that her impersonation would succeed perfectly.
The illusion was simpler, of course, than appeared on the surface. The house was there, completely furnished, ready for use. All that was necessary was to take the boards down, air the place out, clean up, put fresh linen in. There was plenty of time before Alice’s arrival for this preparatory work.
The one weakness of Olivia Fell’s plot was objective, not personal. That woman would have succeeded in anything. But she made the mistake of selecting Nick Keith for the job of murdering Alice Mayhew. Keith had originally insinuated himself into the circle of plotters, posing as a desperado prepared to do anything for sufficient pay. Actually, he was the son of Sylvester Mayhew’s second wife, who had been so brutally treated by Mayhew and driven off to die in poverty.
Before his mother expired she instilled in Keith’s mind a hatred for Mayhew that waxed, rather than waned, with the ensuing years. Keith’s sole motive in joining the conspirators was to find his stepfather’s fortune and take that part of it which Mayhew had stolen from his mother. He had never intended to murder Alice — his ostensible role. When he carried her from the house that first evening under the noses of Ellery and Thorne, it was not to strangle and bury her, as Olivia had directed, but to secrete her in an ancient shack in the nearby woods known only to himself.
He had managed to smuggle provisions to her while he was ransacking the Black House. At first he had held her frankly prisoner, intending to keep her so until he found the money, took his share, and escaped. But as he came to know her he came to love her, and he soon confessed the whole story to her in the privacy of the shack. Her sympathy gave him new courage; concerned now with her safety above everything else, he prevailed upon her to remain in hiding until he could find the money and outwit his fellow-conspirators. Then they both intended to unmask Olivia.
The ironical part of the whole affair, as Mr. Ellery Queen was to point out, was that the goal of all this plotting and counterplotting — Sylvester Mayhew’s gold — remained as invisible as the Black House apparently had been. Despite the most thorough search of the building and grounds no trace of it had been found.
“I’ve asked you to visit my poor diggings,” smiled Ellery a few weeks later, “because something occurred to me that simply cried out for investigation.”