We rushed along the pavement, bare-headed as we were, and at the far corner we found a policeman standing.
"'A robbery has been committed,' I gasped. 'A document of immense value has been stolen from the Foreign Office. Has any one passed this way?'
"'I have been standing here for a quarter of an hour, sir,' said he; 'only one person has passed during that time--a woman, tall and elderly, with a Paisley shawl.'
"'Ah, that is only my wife,' cried the commissionnaire; 'has no one else passed?'
"'Then it must be the other way that the thief took,' cried the fellow, tugging at my sleeve.
"'But I was not satisfied, and the attempts which he made to draw me away increased my suspicions.
"'Which way did the woman go?' I cried.
"'I don't know, sir. I noticed her pass, but I had no special reason for watching her. She seemed to be in a hurry.'
"'How long ago was it?'
"'Oh, not very many minutes.'
"'Within the last five?'
"'Well, it could not be more than five.'
"'You're only wasting your time, sir, and every minute now is of importance,' cried the commissionnaire; 'take my word for it that my old woman has nothing to do with it, and come down to the other end of the street. Well, if you won't, I will.' And with that he rushed off in the other direction.
"But I was after him in an instant and caught him by the sleeve.
"'Where do you live?' said I.
"'16 Ivy Lane, Brixton,' he answered. 'But don't let yourself be drawn away upon a false scent, Mr. Phelps. Come to the other end of the street and let us see if we can hear of anything.'
"Nothing was to be lost by following his advice. With the policeman we both hurried down, but only to find the street full of traffic, many people coming and going, but all only too eager to get to a place of safety upon so wet a night. There was no lounger who could tell us who had passed.
"Then we returned to the office, and searched the stairs and the passage without result. The corridor which led to the room was laid down with a kind of creamy linoleum which shows an impression very easily. We examined it very carefully, but found no outline of any footmark."
"Had it been raining all evening?"
"Since about seven."
"How is it, then, that the woman who came into the room about nine left no traces with her muddy boots?"
"I am glad you raised the point. It occurred to me at the time. The charwomen are in the habit of taking off their boots at the commissionnaire's office, and putting on list slippers."
"That is very clear. There were no marks, then, though the night was a wet one? The chain of events is certainly one of extraordinary interest. What did you do next?
"We examined the room also. There is no possibility of a secret door, and the windows are quite thirty feet from the ground. Both of them were fastened on the inside. The carpet prevents any possibility of a trap-door, and the ceiling is of the ordinary whitewashed kind. I will pledge my life that whoever stole my papers could only have come through the door."
"How about the fireplace?"
"They use none. There is a stove. The bell-rope hangs from the wire just to the right of my desk. Whoever rang it must have come right up to the desk to do it. But why should any criminal wish to ring the bell? It is a most insoluble mystery."
""Certainly the incident was unusual. What were your next steps? You examined the room, I presume, to see if the intruder had left any traces--any cigar-end or dropped glove or hairpin or other trifle?"
"There was nothing of the sort."
"Well, we never thought of that."
"Ah, a scent of tobacco would have been worth a great deal to us in such an investigation."
"I never smoke myself, so I think I should have observed it if there had been any smell of tobacco. There was absolutely no clue of any kind. The only tangible fact was that the commissionnaire's wife-Mrs. Tangey was the name--had hurried out of the place. He could give no explanation save that it was about the time when the woman always went home.