“I don’t know much about the case yet,” said the lieutenant, “but, jumping at a conclusion, I should say that this sneaking chap was jealous of your intimacy with the Minford family; that he wrote the anonymous letters to the old man, in a different hand, and that he either committed the murder, or knows something about it.  His motive for annoying Miss Minford I can understand—­for this city is full of just such well dressed scoundrels; but the motive of the murder I can’t comprehend.  But mark me—–­ this fellow has some knowledge of it; and we must hunt him up.  And, first, let us compare the letters.”

Marcus handed the two letters to the lieutenant, who, with Overtop and Maltboy, gave them a close examination.  One was written on faint blue paper in a buff envelope; the other on white paper in a white envelope.  Every curve, cross, and dot was minutely compared; but not the faintest resemblance between the two letters could be discovered.  “No more like than chalk and cheese,” said the lieutenant.  “My theory is knocked on the head.”

“Let me examine the envelopes again,” said Overtop.  They had inspected them less carefully than the contents.

As soon as Overtop had placed the two envelopes side by side, his eyes lighted up with the pleasure of a great discovery.  “What fools we are!” he exclaimed.  “There it is!  Don’t you see?  Don’t you see?  A regular Hogarthian line of beauty under the name on each.”

All stared at the envelopes, and at once recognized the similarity between the graceful curved lines.  They looked somewhat like the letter S laid on its side; and more like the arm of a rocking chair.

Marcus had a sudden inward vision of the writer.  One of those convictions which defy all logical analysis flashed upon his mind.

“Do you know where this strange young man lives, Bog?” asked Marcus.

“No, sir.  I follered—­I should say followed—­him two or three times, because I thought he wasn’t acting just right toward Miss Minford (here Bog blushed).  He always went into drinking houses and billiard saloons, and once into a place where they say the worst kind o’ gambling is allers—­I mean always—­going on.  But he knew me by sight, and I was afraid he would ask me about that letter which I didn’t deliver for him.  So I had to follow him a good piece behind; and sometimes I lost track of him.  Then, again, he would keep a tramping round from one drinking place to another—­but never getting drunk that I could see—­till twelve or one o’clock at night.  By that time I felt I ought to go home, and so I never tracked him to his lodgings, if he has any.  But it’s my belief he travels in the night, and sleeps in the daytime, like the cats.”

“Good, so far,” said Marcus.  “You have already given us a general description of this fellow’s dress and appearance.  Now, tell me whether his face is pale, his mustache small and curved up in points, his eyes light gray, and never looking straight at you; his nose small, thin, and sharp; and, now I think of it, has he not got a small scar on one of his cheeks?”