The boys reached the post-office about nine o'clock and Nat mailed his letter.
"It's early to go back," said Jack. "Isn't there something that we can do?"
"There's a moving picture show in town," said John. "Let's go to it for awhile."
This was voted a good idea. The boys enjoyed the scenes thrown on the screene, and were particularly taken with a depiction of a cowboy roping a steer.
"That's what we'll soon see in reality," whispered Nat.
They started through the village, and, as they turned down a quiet street that led toward Washington Hall, Jack saw a dark figure sneaking along on the opposite side, in the shadow of some buildings.
"Looks as if some one was following us," said Jack to himself.
As our hero pulled out his handkerchief there flew out with it a letter. The sight of it reminded him that he had promised Professor Hall to mail it that evening. It had slipped his mind, even though he had been in the post-office.
"I'd better run right back with it," said Jack. "Mighty stupid of me.
Well, there's no help for it, and I don't want to disappoint Hall.
He's a good friend of ours."
He picked the letter up, and held it in his hand to insure that it would not be forgotten again.