“Before the police come—­you’ve a chance, Bobby—­the last chance.  You must do before the police arrive whatever is to be done.”

He replaced the shade and glanced at her, astonished by her intensity, by the forceful gesture with which she grasped his arm.  For the first time since Silas Blackburn’s murder all of her vitality had come back to her.

“What do you mean?”

She pointed to the door of the private staircase.

“Just what Howells told you before he went up there to his death.”

Bobby understood.  He reacted excitedly to her attitude of conspirator.

“He said,” she went on, “that the criminal had nothing to lose.  That it would be to his advantage to have him out of the way, to destroy that evidence.”

“I thought of it,” Bobby answered, “just before I went to sleep.”

“Don’t you see?” she said.  “If you had killed him you would have taken the cast and the handkerchief and destroyed them?  Hartley has told me everything, and I could see his coat for myself.  The cast and the handkerchief are still in Howells’s pocket.”

“Why should I have killed him if not to destroy those?” Bobby took her up with a quick hope.

“You didn’t,” she cried.  “Nothing would ever make me believe that you killed him, but you will be charged with it unless the evidence—­disappears.  You’ll have no defence.”

Bobby drew back a little.

“You want me to go there—­and—­and take from his pocket those things?”

She nodded.

“You remember he suggested that he hadn’t sent his report.  That may be there, too.”

Bobby shook his head.  “He must have said that as a bait.”

“At the worst,” she urged, “a report without evidence could only turn suspicion against you.  It wouldn’t convict you as those other things may.  You must get them.  You must destroy them.”

Graham slipped quietly in and closed the door.

“The district attorney is coming himself with another detective,” he said.  “I can guess what Katherine has been talking about.  She’s right.  I’m a lawyer, an I know the penalty of tampering with evidence.  But I don’t believe you’re a murderer, and I tell you as long as that evidence exists they can convict you.  They can send you to the chair.  They may arrest you and try you anyway on his report, but I don’t believe they can convict you on it alone.  You’re justified in protecting yourself, Bobby, in the only way you can.  No one will see you go in the room.  We’ll arrange it so that no one can testify against you.”

Bobby felt himself at a cross roads.  During the commission of those crimes he had been unconscious.  If he had, in fact, had anything to do with them, his personality, his real self, had known nothing, had done no wrong.  His body had merely reacted to hideous promptings whose source lurked at the bottom of the black pit.  To tamper with evidence would be a conscious crime.  All the more, because of his doubt of himself, he shrank from that.  Katherine saw his hesitation.