For, the paper he had picked up was part of an envelope like those which had contained the letters Grace received from her father.  And on the scrap was her name, but the envelope had been spoiled by a blot of ink in writing the address.  It had been torn up and thrown away, to remain a mute bit of evidence.

“Mah Retto knows Mr. Potter!” exclaimed Larry.  “Retto is the man who mailed the letters for the missing millionaire.  If I find him I can make him tell me where Mr. Potter is!  Now to trace my mysterious East Indian friend!”

CHAPTER XXI

TRACING RETTO

Larry took another survey of the apartment to see if there were any more clues that might aid him.  But the one that had so unexpectedly come to his hand was all he found.  The place showed evidences of having been hastily vacated.

“I’ll see Mr. Jackson,” he decided.  “Perhaps he can tell me something.  He was interested in this queer man.”

He lost no time in going to the rooms of his friends.  They were glad to see him, and asked a number of questions about his mother, sisters and brother.  But Larry, as soon as he could, turned the subject to Retto.

“He’s gone,” he told Mr. Jackson.

“I supposed he had.  I saw the janitor taking his things from the room this morning.”

“Do you know where he went to?” asked the young reporter eagerly.  “I want to find him.”

“I haven’t the least idea.”

“I wonder if the janitor would know,” Larry went on.

“He might.  Perhaps the man left his address with him, in order that letters might be forwarded.  I’ll go downstairs with you and introduce you to the janitor.”

That functionary was unable to throw any light on where Retto had gone.  Evidently, for the time being, the chase had come to an end.

Larry made his way to the nearest elevated station and rode in the direction of the Potter home.  He had no definite plan in mind, and, more from a whim than anything else, he decided to walk past the house.  He did not expect it, but he had an idea—­a very faint one—­that he might see Grace.  Of course, if he saw her at the window, where she sometimes sat, it would be no more than polite to go in and tell her what the carrier had said about the second letter.

When Larry got in front of the Potter house he was disappointed to see that it was in darkness.  It was about ten o’clock, and he knew the family was in the habit of retiring early, especially since Mr. Potter’s disappearance.

As he strolled past on the other side of the street, looking in vain for a glimmer of light, or the sight of a girlish face against the window pane, he passed into the deep shadow cast by a big tree on which shone an electric arc light in front of the Potter house.  The blackness was quite deep, in contrast to the illumination on both sides of the tree, for electric lamps have the property of casting dense shadows.  If Larry had been looking straight in front of him perhaps it would not have happened, but he was staring at where Grace lived, and the first thing he knew he had walked full tilt into a man who was hiding in the darkness behind the big tree.