"And the discovery?" I asked impatiently. "What's its nature?" "Most astounding," he replied, with a bewildered look. "I'm a police officer, Urwin," he added hoarsely, "and I'm not often unnerved. But to-night, by Jove! I'm upset--altogether upset. The whole affair is so devilish uncanny and unnatural." "Tell me the story," I urged. "If it is so strange the evening papers will have a good time to-morrow." "No, no," he cried in quick alarm. "You must publish nothing yet-- nothing. You understand that I give you these facts only on condition that you promise not to publish any thing until I give you permission. You alone will know of it. We must preserve the utmost secrecy. Not a word must leak out yet. You understand in what an awkward position you would place me were you to publish anything of this affair." "Of course. I promise you to keep the matter a strict secret," I answered. "There are many cases in which the publication of the details of a crime might defeat the efforts of the police, and this I supposed to be one of them." "Well," he said, "I made the discovery in a most curious manner. Just before seven o'clock this evening, just as it was growing dark, I was returning to the station after visiting the `fixed-point' at the corner of Earl's Court Road. You know the spot--just opposite Holland Park." I nodded. I knew that particular street-corner where Earl's Court Road joined Kensington Road quite well. "I had previously been my usual round through Campden Hill Road and Holland Walk, and was strolling back along the main Kensington Road, past that terrace of houses Upper Phillimore Place, when my attention was suddenly arrested by seeing on the steps leading from the pavement up to the front garden of one of the houses a small object moving. It was inside the gate, and in the dim half-light I bent to examine it. What do you think it was?" "Don't know," I replied. "Don't ask riddles--describe facts." "Well, it was the very last thing one would dream of finding on a London doorstep--a small, strangely-marked snake." "A snake!" I echoed. "You didn't arrest it for being found without visible means of subsistence, I suppose?"