Collins seemed glad of even this slight concession on the part of the boy, and walked along briskly.  Presently, however, he began to fall back, talking with Jimmie, who was a few paces behind.  Then, before very long, the little fellow missed Collins.  He had disappeared in a dark alley.  Ned worried over this when informed of the fellow's strange and contradictory conduct.  The man might have gone to make report to the other aviator!  This was not a pleasant reflection.