The Phantom’s face darkened a trifle. “I advanced the idea only as a hypothesis,” he declared a little testily, “and as yet I am not at all sure that it has any value. For instance, in order to reach Gage’s bedroom by way of the tunnel, the murderer had to go through your house and get down in the cellar.”
“Which could easily be done. Both Jerome and myself are sound sleepers and the house has no burglar protection.”
“But that isn’t all. After traversing the tunnel, the murderer had to enter the bedroom. In order to do so he had to work the mechanism which controls the revolving window frame. From the inside of the chamber it is worked by the nail. Can it be manipulated from the outside as well?”
“Dear me!” exclaimed the doctor, almost jumping out of the chair. “I never thought of that.”
The Phantom eyed him keenly, though he seemed wholly absorbed in contemplation of the salt shaker. The exclamation, he thought, had not sounded quite natural.
“You invented the contraption,” he pointed out. “Surely you ought to know whether the mechanism can be worked by a man approaching the room by way of the tunnel.”
“So I thought. An inventor ought to know the children of his brain.” He gave a forced chuckle, as if fencing for time in which to frame an answer. “The fact of the matter is that the contrivance was intended to be an emergency exit and nothing else. The spring by which the mechanism is operated can’t be reached by a man approaching the room by way of the tunnel. But that,” with a grin which wrinkled his whole face, “does not exclude the possibility of a man getting through by the use of force. For instance, the frame could be budged by prying.”
“Perhaps. As matters stand, the whole question hinges on whether the room can be entered from the tunnel. If it can’t, then it is certain that Pinto committed the murder. If it can, there is a possibility that someone else did it, though the preponderance of evidence still points in Pinto’s direction, for it is extremely unlikely that the murderer was aware of the existence of the tunnel. However——”
He checked himself, deciding to let the thought remain unspoken. The anthropologist, having recovered from his temporary embarrassment, gave a hearty laugh.
“You are incorrigible, my friend. You are willing to admit almost any theory but the plain and obvious one, which is that the Gray Phantom committed the murder. Reminds me of Pinel’s excellent treatise on the psychology of the criminal. But you must be tired. Please excuse me while I make a telephone call.”