“Irrational,” Doctor Groom answered, “must not be confused with impossible.  The marks of a physical violence, far from proving that the attack was physical, strengthens the case of the supernatural.  Certainly you have heard and read of pictures being dashed from walls by invisible hands, of objects moved about empty rooms, of cases where human beings have been attacked by inanimate things—­heavy things—­hurtling through the air.  Some scientists recognize such irrational possibilities.  Policemen don’t.”

“Very well,” Graham said stubbornly.  “I’ll follow you that far, but you must show me in this room the sharp object with which these men were attacked, no matter what the force behind it.”

The doctor spread his hands.  His infused eyes nearly closed.

“That I can’t do.  At any rate, Robert, this isn’t wholly tragic to you.  I don’t see how any one could accuse you of aphasia to-night.”

“You’ve not forgotten,” Bobby said slowly, “that you spoke of a recurrent aphasia.”

“That’s the trouble,” Graham put in under his breath.  “He has no more alibi now than he had when his grandfather was murdered.”

Bobby told of his heavy sleep, of the delay in Katherine’s arousing him.

The doctor’s gruff voice was disapproving.

“You shouldn’t have drunk that medicine.  It had stood too long.  It would only have approximated its intended effect.”

“You mean,” Bobby asked, “that I wasn’t sleeping as soundly as I thought?”

“Probably not, but you’re by no means a satisfactory victim.  Men do unaccountable things in a somnambulistic state, but asleep they haven’t wings any more than they have awake.  You’ve got to show us how you entered this room without disturbing the locks.  Now, Mr. Graham, we must comply with the law.  Call in the police.”

“There’s nothing else to do,” Bobby agreed.

So they went along the dingy corridor and downstairs.  From the depths of the easy chair in which Paredes lounged smoke curled with a lazy indifference.  The Panamanian didn’t move.

While Graham and the doctor walked to the back of the hall to telephone, Katherine, an anxious figure, a secretive one, beckoned Bobby to the library.  He went with her, wondering what she could want.

It was quite dark in the library.  As Bobby fumbled with the lamp and prepared to strike a match he was aware of the girl’s provocatively near presence.  He resisted a warm impulse to reach out and touch her hand.  He desired to tell her all that was in his heart of the division that had increased between them the last few months.  Yet to follow that impulse would, he realized, place a portion of his burden on her shoulders; would also, in a sense, be disloyal to Graham, for he no longer questioned that the two had reached a definite sentimental understanding.  So he sighed and struck the match.  Even before the lamp was lighted Katherine was speaking with a feverish haste: