Some little time after this Mark was intrusted by his chief with the work of discovering a man who had committed a very atrocious murder, and was, it was tolerably certain, hiding in the slums of Westminster.

It was the first business of the kind that had been confided to him, and he was exceedingly anxious to carry it out successfully.

He dressed himself as a street hawker, and took a small lodging in one of the lanes, being away the greater portion of the day ostensibly on his business, and of an evening dropped into some of the worst public houses in the neighborhood.

He was at first viewed with some suspicion, but it was not long before he became popular.

He let it be understood that he had got into trouble down in the country, and that he was quite ready to take part in any job that promised to be profitable.