t. Only 'Phemie, it will be remembered, had
the midnight adventure in the old doctor's suite of offices in the east
wing.

Lyddy only said, occasionally, that it was odd Aunt Jane had not sent the
key to the green door when she expressed all the other keys to her nieces
when the project of keeping boarders at Hillcrest was first broached.

At these times 'Phemie had kept as still as a mouse. Sometimes the key
was worn on a string around her neck; sometimes it was concealed in a
cunning little pocket she had sewn into her skirt. But wherever it was,
it always seemed--to 'Phemie--to be burning a hole in her garments and
trying to make its appearance.

After finding Professor Spink filling the bottles with water up by
Pounder's Brook, the girl was more than usually troubled about the east
wing and the mystery.

She moved the key about from place to place. One day she wore it; another
she hid it in some corner. And finally, one night when she came to go to
bed, she found that the cord on which she had worn the key that day was
broken and the key was gone.

She screamed so loud at this discovery that her sister was sure she had
seen a mouse, and she bounded into bed, half dressed as she was.

"Where--where is it, 'Phemie?" she gasped, for Lyddy was as afraid of mice
as she was of rats.

"Oh, mercy me!" wailed 'Phemie, "that's what I'd like to know."

"Didn't you see it?" cried her trembling sister.

"It's gone!" returned 'Phemie.

Lyddy got gingerly down from the bed.

"Then I'd like to know what you yelled so for--if the mouse has
disappeared?" she demanded, quite sternly.

And then 'Phemie, understanding her, and realizing that she had almost
given her secret away, burst into a hysterical giggle, which nothing but
Lyddy's shaking finally relieved.

"You're just as twittery as a sparrow," declared Lyddy. "I never _did_
see such a girl. First you're squealing as though you were hurt, and then
you laugh in a most idiotic way. Come! do behave yourself and go to bed!"

But even after 'Phemie obeyed she could not go to sleep.

Suppose somebody picked up that key? She had no idea, of course, where
it had been dropped. Certainly not on the floor of her bedroom. Some time
during the day, inside, or outside of the house, the key, with its little
brass tag stamped with the words "East Wing," had slipped to the ground.

Now--suppose it was found?

'Phemie got out of bed quietly, slipped on her slippers and shrugged