knew the terrible history of the girl's father, and perhaps had lived in fear of some criminal outcropping in the child."
There was a silence for several moments. Each of us was busy with his own thoughts. Then Vance continued:
"After Mrs. Greene's death, only Sibella stood between Ada and her blazing goal; and it was Sibella herself who gave her the idea for a supposedly safe way to commit the final murder. Weeks ago, on a ride Van and I took with the two girls and Von Blon, Sibella's venomous pique led her to make a foolish remark about running one's victim over a precipice in a machine; and it no doubt appealed to Ada's sense of the fitness of things that Sibella should thus suggest the means of her own demise. I wouldn't be at all surprised if Ada intended, after having killed her sister, to say that Sibella had tried to murder her, but that she had suspected the other's purpose and jumped from the car in time to save herself; and that Sibella had miscalculated the car's speed and been carried over the precipice. The fact that Von Blon and Van and I had heard Sibella speculate on just such a method of murder would have given weight to Ada's story. And what a neat ending it would have made—Sibella, the murderer, dead; the case closed; Ada, the inheritor of the Greene millions, free to do as she chose! And—'pon my soul, Markham!—it came very near succeeding."
Vance sighed, and reached for the decanter. After refilling our glasses he settled back and smoked moodily.
"I wonder how long this terrible plot had been
