about, but with her arm still in a sling. For some reason, however, the girl appeared almost farouche when approached by him. One day when we were at the house Von Blon called, and Vance seemed to go out of his way to hold him in conversation.
As I have said, I could not fathom his motive in all this apparently desultory social give-and-take. He never broached the subject of the tragedies except in the most indirect way; he appeared, rather, to avoid the topic deliberately. But I did notice that, however casual his manner, he was closely studying every one in the house. No nuance of tone, no subtlety of reaction, escaped him. He was, I knew, storing away impressions, analyzing minute phases of conduct, and probing delicately into the psychological mainsprings of each person he talked to.
We had called perhaps four or five times at the Greene mansion when an episode occurred which must be recounted here in order to clarify a later development of the case. I thought little of it at the time, but, though seemingly trivial, it was to prove of the most sinister significance before many days had passed. In fact, had it not been for this episode there is no telling to what awful lengths the gruesome tragedy of the Greenes might have gone; for Vance—in one of those strange mental flashes of his which always seemed wholly intuitive but were, in reality, the result of long, subtle reasoning—remembered the incident at a crucial moment, and related it swiftly to other incidents which in themselves appeared trifling, but which, when co-ordinated, took on a tremendous and terrible importance.
