The muffled whir of her alarm clock awakened Betty. For a moment she was
dazed, then recollection cleared her mind. She slipped to the floor
without waking Bobby and softly tiptoed from the room.

A dim light burned in the corridor, and Betty knew the way to the water
tower. To reach it, one had to mount to the roof of the dormitory
building. Betty experienced a little difficulty with the obstinate catch
of the scuttle cover, but she finally mastered it and stepped out on the
tarred graveled roof. The water tower, a huge tank on an iron framework,
had a little enclosed room built directly under it reached by an iron
ladder. Here the engineer kept various plumbing tools. It was in this
room that Betty was to leave the card.

The night wind blew damp and keen, and the stars overhead seemed very far
away. Betty had no sense of fear as she began to climb, mounting slowly
and feeling for each step with her hands. The friendly dark shut in
around her and somewhere in the distance a train whistle tooted shrilly.

She knew she had reached the last step when her hands encountered wood,
and she felt about till she touched the knob of the door. It opened at
her touch and she pulled herself in over the sill.

"Now the card," she whispered, feeling in her pocket.

A gust of wind fanned her cheek and something clicked.

The door had blown shut!

CHAPTER XXI

DRAMATICS

There are pleasanter places to be at midnight than the dark room of a
strange water tower, but Betty was not frightened. She tripped over some
tool as she felt for the door and discovered that she had lost her sense
of direction completely.

"I'm all turned around," was the way she expressed it. "I must start and
go around the sides, feeling till I come to the door."

Following this plan, she did come to the door and confidently turned the
knob. The door stuck and she rattled the knob sharply. Then the
explanation dawned on her.

The door was locked!

Could it have a spring lock? she wondered. Then she remembered a day
when, on exploration bent, a group of girls had made the trip to the roof
and the kindly Dave McGuire had taken a key from his pocket and unlocked
the door of the little room for the more adventurous ones who wanted to
climb up and see the inside.

"It was a flat key, like a latch key," Betty reflected. "The girls must
have had the door unlocked for me to-night, but I don't think they would
follow me and lock it. That would b