Then in a panic she realized that whatever it was had started upstairs.

Nearer, nearer came the stealthy padding, till Billie realized it had
reached the landing. Her scalp crept and her hair began to stand on end.
Her door was the nearest to the stairs, and she was all alone in the
house with Chet!

Swiftly, she threw off the covers, jumped out of bed, and with her
limbs trembling under her, ran to the door and softly turned the key
in the lock.

Then she leaned weakly against the door and listened for the noise, but
it had stopped. Evidently the burglar, if burglar it was, had paused to
get his bearings.

Then another horrible thought struck her. Chet was sleeping in the next
room, and Chet's door was unlocked!

On feet that seemed too weak to hold her she crept into Chet's
room--luckily there was a connecting door between--and softly turned the
key in his door also.

Evidently she was just in time, for as she listened the stealthy noise
began again and it was coming toward the very door she had just locked.

She uttered a little involuntary sound, and Chet sat up in bed
with a start.

"Wh-what's up?" he demanded sleepily.