. But she heard a
sound below--in the lower hall. Somebody was fumbling with the chain of
the front door.

"He's going out! I declare, he's going out!" thought Ruth and sped
to the window.

She heard the jar of the big front door as it was opened, and then pulled
shut again. She heard no step on the porch, but a figure soon fluttered
down the steps. It was not Isadore Phelps, however. Ruth knew that at
first glance. Indeed, it was not a boy who started away from the house,
running on the grass beside the graveled walk.

Ruth turned back hastily and looked at the other bed--at Mercy's bed.
The place beside the lame girl was empty. Nita had disappeared!

CHAPTER XVIII

ANOTHER NIGHT ADVENTURE

Ruth was startled, to say the least, by the discovery that Nita was
absent. And how softly the runaway girl must have crept out of bed and
out of the room for Ruth--who had been awake--not to hear her!

"She certainly is a sly little thing!" gasped Ruth.

But as she turned back to see what had become of the figure running
beside the path, the lantern light was flashed into her eyes. Again the
beam was shot through the window and danced for a moment on the wall
and ceiling.

"It is a signal!" thought Ruth. "There's somebody outside besides
Nita--somebody who wishes to communicate with her."

Even as she realized this she saw the lantern flash from the dock. That
was where it had been all the time. It was a dark-lantern, and its ray
had been intentionally shot into the window of their room.

The figure she had seen steal away from the bungalow had now disappeared.
If it was Nita--as Ruth believed--the strange girl might be hiding in
the shadow of the boathouse.

However, the girl from the Red Mill did not stand idly at the window
for long. It came to her that somebody ought to know what was going on.
Her first thought was that Nita was bent on running away from her new
friends--although, as as far as any restraint was put upon her, she might
have walked away at any time.

"But she ought not to go off like this," thought Ruth, hurrying into
her own garments. By the faint light that came from outside she could
see to dress; and she saw, too, that Nita's clothing had disappeared.

"Why, the girl must have dressed," thought Ruth, in wonder. "How could
she have done it with me lying here awake?"

Meanwhile, her own fingers were busy and in two minutes from the time she
had turned from the window, she opened the h