“Maybe,” said Billie skeptically, “but hers is so small you would need a microscope to see it.  There’s the janitor now, just going out.  If we run we can catch him.”

And run they did, presenting themselves a minute later, rather red in the face and out of breath, before a very much amused janitor.

“Hello,” he cried, his twinkling eyes under their shaggy brows lighting with pleasure as he looked at the girls.  “Are you young ladies tryin’ to catch a train, or what?”

“Oh, no, no,” cried Violet eagerly.  “We were just trying to catch you, Mr. Heegan.”

“Oh-ho!  An’ it’s mighty flattered I am,” said Mr. Heegan, his Irish brogue coming to the fore.  “An’ what, if I might be askin’ you—­”

“It’s a book we left here,” Billie broke in quickly.  “Laura wants to know if you will let us in long enough to get it.”

“Sure, an’ I will that,” Mr. Heegan assured them, leading the way into the school yard and pulling out his bunch of keys.  “It must be a verra important book,” he added, smiling at them as he fitted the key in the lock, “to be bringing you back to school after school’s out.”

“It was a gift from Father,” Laura explained.  “And I wouldn’t lose it for anything.”

“All right, there you go,” said the good-natured janitor, swinging the door wide for them.  “I’m goin’ home, but I’ll be comin’ back in a few minutes to lock up.  You’d best not be stayin’ here then,” he added, with a twinkling backward glance at them, “or it will be locked up for the night you’ll be.”

“We won’t be more than a minute,” Violet assured him, and jubilantly the girls ran through the empty, echoing hall and stopped before a door at the farther end.

“It seems so horribly quiet,” said Violet, looking around at them with her hands on the door knob.  “It makes you feel like a thief.”

“Must be your guilty conscience,” said Laura wickedly.  “Come on, Vi; we’ve got to hurry if we don’t want to be ‘locked in for the night.’”

“Are you sure you left the book here, Laura?” asked Billie, as Violet opened the door and they crowded in.  “It would be too bad if it were gone—­”

But a cry from Laura interrupted her.

“There it is,” she said, running to a desk at the farther end of the room and picking up from an inner corner a prettily bound book.  “Just the very place I left it, too.  My, but I’m glad to get it back again.”

“What do you think you’re doing, Billie Bradley?” inquired Laura a minute later, for Billie had seated herself at the teacher’s desk and was looking as severe as she knew how.

“Take your seats,” she now commanded, rapping vigorously on the desk and fixing them with her best school-teacher stare.  “Violet Farrington, go to the board—­”

But she got no further, for with an indignant cry the girls had rushed on her.  Dropping both her air of command and her dignity, Billie scurried wildly around the room, keeping the desks between her and her pursuers.