Nevertheless the sudden change in the expression of his face at the moment of the outbreak was remarkable. The previously smooth and unpuckered brows gathered themselves together into two diagonal wrinkles that met above the nose, which had in the meantime become beak-like, and the effect recalled in some curious way a bird of prey. He was soon all smiles again; but once or twice throughout the journey, when his thoughts were presumably unpleasant, I caught the same expression, and it was the fact of my seeing in the photograph this same unmistakable expression on the face of a man who was apparently a different person which had set me fumbling with such uncertain hand among the dog’s-eared pages of the past. The eyes, the hawk-like wrinkling of the brows, and the nose and nostrils were of course the same, but the addition of the beard, the evident swarthiness of the skin, and darkening of the hair led to my failing at first to connect the portrait with my fellow-passenger to Southend. But the missing link was no sooner found and the connection established than I felt that the identity of Mullen with the man I had seen in the train admitted of no uncertainty, especially as, after examining under a powerful lens, the photograph which the informer had given to the police, I satisfied myself that the beard was false. My next step was to set on foot an inquiry into Mullen’s family history and antecedents. I hoped, and in fact believed, that the clue which I held to his identity would in itself enable me to trace him, but at the same time I fully recognised that circumstances might arise which would render that clue useless and throw me back upon such information as could be ascertained apart from it. That I should not be unprepared for such a contingency was very necessary, and I therefore commissioned a private detective named Green, whom I knew to be able and trustworthy, to ferret out for me all that could be discovered of Mullen’s past. Having wished him good-bye and good luck, I started for Southend, whither I intended journeying in the company of the little talkative man with whom Mullen had had the brush about the fusees. I thought it more than likely that he was a commercial traveller, partly because of the deferential stress and frequency with which he interpolated the word “sir” into any remarks he chanced to make, and partly because of the insinuating politeness with which he addressed Mullen and myself--politeness which seemed to suggest that he had accustomed himself to look upon every one with whom he came into contact as a possible customer, under whose notice he would one day have occasion to bring the excellence of his wares, and with whom, therefore, he was anxious to be on good terms.