Dr. Pye did not answer, but bringing forward the small box, opened it, and sent a flashlight straight into the opposite window. "God in heaven!" he cried, falling back affrighted. In that brief moment of light he had seen at the window the face and form of Samuel Boyd! CHAPTER XLI. HOW A MURDERER MIGHT HAVE BEEN DISCOVERED. Dr. Vinsen vainly seeking in the darkness for the cause of Dr. Pye's alarm, could not utter a word. In his listening attitude, with the white fear depicted on his countenance, he presented a terror-struck appearance, and seemed to be waiting for advancing footsteps, or for the sound of voices in the street without, demanding admittance. But the silence was not broken. "Can't you speak?" he then said in a whisper to his companion. "What is it? Is there anybody in the Square? Turn up the light." His hand was groping for the tap that controlled the gas when Dr. Pye seized his arm and held him back. Dr. Vinsen winced and impatiently endeavoured to free himself, but the fingers that had fastened themselves upon his muscles were more like rods of steel than flesh and bone. "Let go!" he muttered. "You are crushing my arm." "Do not stir," replied Dr. Pye, releasing him. Then he masked the shutter, and brought light into the room. It was characteristic of this man that, short as had been the interval between his startled exclamation and the lighting up of the apartment, he had regained his self-control, and that on his features no trace of his recent agitation was visible. There are moments of unexpected surprise when the fixed habits of a carefully trained life slip their hold, and the mind becomes as unquestioningly receptive as that of a child. Such a moment had come to Dr. Pye when he beheld the vision of the man the mystery of whose death was on every tongue. It held him only for the moment; before the passing of another his dominant will had reasserted itself, and his face resumed his impenetrable calm. "Now, what is it?" again demanded Dr. Vinsen. His eyes travelled round the room, and colour came into his cheeks when he saw they were alone. "You did not see it?" replied Dr. Pye. "See what?" "The figure of Samuel Boyd standing at his window?" Dr. Vinsen stared incredulously at his host, and then a long deep breath of relief escaped him. "Only that!" he exclaimed. "I thought it was something worse." Dr. Pye repeated his question. "You did not see it?" "I saw nothing. The dead do not rise from their graves. Dead once, dead for ever. But you can convince me by producing ocular proof. Your ingenious device takes an instantaneous picture of any object upon which it flashes its light. Produce me the picture of the dead and buried Samuel Boyd." "I cannot. The last film has been used, and I omitted to put in others." "Very unfortunate," said Dr. Vinsen, dryly. "Suppose you supply the omission, and try again."