“Yes,” Paredes said.  “Perhaps we shouldn’t have left him alone.  Let us go back.  Let us see if he is all right.”

Rawlins laughed skeptically.

“You’re not afraid he’ll melt away!”

“I’m not so sure he won’t,” Paredes answered.

They followed him downstairs.  Because of the position of Blackburn’s chair they could be sure of nothing until they had reached the lower floor and approached the fireplace.  Then they saw.  It was as if Paredes’s far-fetched fear had been realized.  Blackburn was not in his chair, nor was he to be found in the hall.  Even then, with the exception of Paredes, they wouldn’t take the thing seriously.  Since the old man wasn’t in the hall; since he couldn’t have gone upstairs, unobserved by them, he must be either in the library, the dining room, or the rear part of the house.  There was no one in the library or the dining room; and Jenkins, who sat in the kitchen, still shaken by the discovery at the grave, said he hadn’t moved for the last half hour, was entirely sure no one had come through from the front part of the house.

They returned to the hall and stood in a half circle about the empty chair, where a little while ago Silas Blackburn had cowered, mouthing snatches of his fear—­“I’m not dead!  I tell you I’m not dead!  They can’t make me go back—­”

The echoes of that fear still shocked their ears.

There was a hypnotic power about the vacancy as there had been about the emptiness in the burial ground.  Paredes spoke gropingly.

“What would we find,” he whispered, “if we went to the cemetery and looked again in the coffin?”

“Why should he have come back at all?” Groom mused.

Robinson opened the front door.

“You know he might have gone this way.”

But already the snow had obliterated the signs of their own passage in and out.  It showed no fresh marks.

“Silas Blackburn has not gone that way in the body,” Doctor Groom rumbled.

The storm was more violent.  It discouraged the idea of examining the graveyard again before morning.

Robinson glanced at his watch.  He led Bobby and the detective to the library.

“Then try your scheme if you want,” he said, “but understand I assume no responsibility.  Honestly, I doubt if it amounts to anything.  You’ll shout out if you are attacked, or the moment you suspect any real cause for fear.  Rawlins will be in the corridor, and I’ll be in the library or wandering about the house—­always within call.  Rawlins will guard the broken door, but be sure and lock the other one.”

The two officers went upstairs with Bobby.  Graham followed.

“You understand,” Robinson said.  “I’d rather Paredes and the doctor didn’t suspect what you are going to do.  Change your mind before it’s too late, if you want.”

Bobby walked on without replying.

“You can’t dissuade him,” Graham said, “because of what will happen to-morrow unless the truth is discovered to-night.”