“So it does.” The doctor seemed not at all disturbed by Vanardy’s sharp gaze. “Years ago, when I was looking for an inconspicuous and out-of-the-way place in which to pursue my studies in quiet, I leased the house to which this laboratory forms an extension. I saw Gage now and then, and the man interested me. Even before we became confidential I had noticed phrenological manifestations that seemed to classify him as belonging to one of the types described by Lombroso. Step by step I became familiar with his history and mode of life. I learned that he was conducting an extensive traffic in stolen goods, and that he had a broad circle of acquaintances in the underworld. Gage proved useful, introducing me to criminals whom I wished to study at close range, and, in addition to that, the man himself interested me. I saw traits and peculiarities in him that were strangely contradictory. And so, when one day he confided to me that he was living in constant fear of the police, who were likely to raid his premises at any time and confiscate his valuables, I made a proposition to him.”
“You offered to help on the condition that he sign his body over to you for dissecting purposes,” guessed the Phantom.
“Exactly, my friend.” Bimble rubbed his hands in glee. “I offered to invent an avenue of escape that would be absolutely safe and proof against detection. Gage accepted, and I set to work fulfilling my part of the bargain. The result, if I may bestow compliments on myself, was a work of genius.”
The Phantom gazed in frank astonishment at the versatile anthropologist. “The police have a nasty name for that sort of thing,” he observed.
“The police and I are friends. I help them on occasions, when the spirit moves me and the case interests me. And a scientific man, my dear sir, cannot afford to have moral scruples. The ends of science justify all other things, even assisting a criminal to escape. Incidentally I derived a lot of entertainment out of the planning of the tunnel. In the first place, the window was purposely built so small that no one would consider it for a moment as a possible means of escape. Still less would any one think of looking for an exit hidden behind the frame of such a window. You noticed the nail, of course. A lot of psychology is centered around that nail.”
“So it’s a psychological nail, eh?” The Phantom looked at the scratch on his wrist.
“I knew, from my observations of the workings of the human mind, that not one person in ten million would give a second thought to that nail. Even if, by remote chance, someone should touch it, he would never suspect that it was a part of a mechanism. If, by a still remoter chance, he would investigate more closely, he would not know how to operate it. So, you see, there is not one chance in a billion that a stranger would find the tunnel. Do you blame me for doubting your statement that you found it by accident?”
The Phantom looked at Miss Hardwick. Doctor Bimble’s explanation seemed to have impressed her strongly. He did not wonder at this, for he knew there was logic in the anthropologist’s argument. Nothing but his firm belief that Gage had provided himself with an emergency exit of some sort had prompted the Phantom to give the nail a closer scrutiny.
Doctor Bimble gave him a mildly amused look.
“You agree with me—don’t you, Vanardy? I think my logic holds together. Only a person familiar with the tunnel could have committed the murder. Conversely, a person betraying a knowledge of the tunnel is a worthy object of suspicion.”