“It must have a foot,” thought the brave captain of the band, as he plunged farther and farther into the depths of the white cave.  “All beds have.”  Then he stopped suddenly as a loud squeal of mingled surprise and terror came from just behind him.

“Oh, Rudolf,” Ann cried, “I don’t want to play this game any longer—­let’s go back!” In the half-darkness Rudolf felt her turn round on Peter, who was close behind her.  “Go back, Peter,” she ordered.

“I can’t,” came a little voice out of the gloom.

“You must—­oh, Peter, hurry!”

“I can’t go back,” said Peter 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.