“You mean,” the doctor answered, “Robert Blackburn.  He was a year younger than Silas.  This boy was named in memory of him.  Why should any one have remembered?  He died in South America more than a quarter of a century ago, before these children were born.”

“That’s what Silas Blackburn told you when he came back,” Paredes said.  “He may have believed it at first or he may not have.  I daresay he wanted to, for he came back with his brother’s money as well as his own—­the cash and the easily convertible securities that were all men would handle in that hell.  But he never forgot that his brother’s wife was alive, and when he ran from Panama he knew she was about to become a mother.

“That brings me to the other feature that made me wander around here like a restless spirit myself that night.  You had just told your story about the woman crying.  If there was a strange woman around here it was almost certainly Maria.  As Rawlins deduced, she must either be hysterical or signalling some one.  Why should she come unless something had gone wrong the night she drugged Bobby to keep him in New York?  She wasn’t his enemy, because that very night she did him a good turn by trampling out his tracks in the court.”

Bobby took Maria’s letter from his pocket and handed it to Paredes.

“Then how would you account for this?”

The Panamanian read the letter.

“Her way of covering herself,” he explained, “in case you suspected she had made you drink too much or had drugged you.  She really wanted you to come to tea that afternoon.  It was after writing that that she found out what had gone wrong.  In other words, she read in the paper of Silas Blackburn’s death, and in a panic she put on plain clothes and hurried out to see what had happened.  The fact that she forgot her managers, her professional reputation, everything, testified to her anxiety, and I began to sense the truth.  She had been born in Panama of a Spanish mother and an American father.  She had some stealthy interest in the Cedars and the Blackburns.  She was about the right age.  Ten to one she was Silas Blackburn’s niece.  So for me, many hours before Silas Blackburn walked in here, the presence of the other Blackburn about the Cedars became a tragic and threatening inevitability.  Had Silas Blackburn been murdered or had his brother?  Where was the survivor who had committed that brutal murder?  Maria had come here hysterically to answer those questions.  She might know.  The light in the deserted house!  She might be hiding him and taking food to him there.  But her crying suggested a signal which he never answered.  At any rate, I had to find Maria.  So I slipped out.  I thought I heard her at the lake.  She wasn’t there.  I was sure I would trap her at the deserted house, for the diffused glow of the light we had seen proved that it had come through the cobwebbed windows of the cellar, which are set in little wells below the level of the ground.