calmly, "because there isn't any back.
Put your hand behind me and feel."

It was true. Just how or when it had happened none of them could tell,
but the soft drooping bedcovers had suddenly, mysteriously risen and
spread into firm white walls behind and on either side, leaving only a
narrow passageway open in front. It was nonsense to go on their hands
and knees any longer, for even Rudolf, who was tallest, could not
touch the arched white roof when he stood up and stretched his arm
above his head. He could not see Ann's face clearly, but he could hear
her beginning to sniff.

"Now, Ann," said he sternly, though in rather a weak voice, "don't you
know what this is? This is an adventure."

"I don't care," sniffed Ann, "I don't want an adventure. I want to go
back--back to Aunt Jane!" And the sniff developed into a flood of
tears.

"Peter is not crying, and he is only six."

This rebuke told on Ann, for she was almost eight. "But what are we
go--going to do?" she asked, her sobs decreasing into sniffs again.

"We'll just have to go on, I suppose, and see what happens."

"Well, I think--I think Aunt Jane ought to be ashamed of herself to
put us in such a big bed we could get lost in it!"

"Maybe"--came the voice of Peter cheerfully from behind them--"maybe
she _wanted_ to lose us, like bad people does kittens."

"Peter, don't be silly," ordered Rudolf sternly. "There isn't really
anything that can happen to us," he went on, speaking slowly and
thoughtfully, "because we all know that we really are in bed. We know
we didn't get _out_, so of course we must be _in_."

This was good sense, yet somehow it was not so comforting as it ought
to have been, not even to Rudolf himself who now began to be troubled
by a disagreeable kind of lump in his throat. Luckily he remembered,
in time to save himself from the disgrace of tears, how his father had
once told him that whistling was an excellent remedy for boys who did
not feel quite happy in their minds. He began to whistle now, a poor,
weak, little whistle at first, but growing stronger as he began to
feel more cheerful. Grasping his sword, he started ahead, calling to
the others to follow him.

The white passage was so narrow that the children had to walk along it
one behind another in Indian file. The floor was no longer soft and
yielding but firm and hard under their feet, and by stretching out
their hands they could almost touch the smooth white walls on either
si