“Are you much hurt, my dear?” cried Hildegarde.  “Wait till I come and pick you up, poor child!”

“Oh no!” replied Gertrude, softly, from the foot of the stairs, where she lay doubled up against the door.  “Thank you, but I never hurt myself.  I hope I haven’t hurt the stairs.”

Bell came along, laughing.  “Dear Dropsy!” she said.  “Here, come up!  She really never does hurt herself,” she added, in response to Hildegarde’s look of astonishment.  “She falls about so much, and has done so since she was a baby, that she keeps in training, I suppose, and her joints and bones are all supple and elastic.  This was a good one, though!  Sure you are not bruised, little girl?”

Gertrude picked herself up, declining assistance, and maintained stoutly that she was sound in wind and limb.  “If only I did not break anything,” she said, anxiously.  “I came a terrible crack against the panel here, and it seemed as if something gave as I fell past it.”

Bell bent down, in spite of Hildegarde’s assurance that everything was right, and passed her hand along the wall of the staircase.  “There is no crack,” she said.  “I think it is all right, Toots.”  She tapped the panel critically.  “The wall is hollow here,” she said.  “Is this your secret chamber, Hildegarde?”

“Hollow?” cried Hildegarde.  “What do you mean, Bell?  I know of no hollow place there.”

“Have you ever looked for one?” Bell inquired.  “Search would reveal something in there, I am pretty sure.”

Thrilled with curiosity, Hildegarde came down, and the three girls crouched together on the narrow stair, and tapped and rapped here and there.  Beyond a doubt, one panel was hollow.  What could it mean?

Bell meditated.  “What is on the other side of this place?” she asked.

“I—­don’t know,” said Hildegarde.  “Stop a moment, though!  It must be,—­yes, it is!  The old chimney, the great square stack, comes near this place.  Can there be any space—­”

“Then it is a secret chamber, most likely,” said Bell.  “I have heard of such things.  Shall we try?”

They tried eagerly, pressing here, pushing there, but for some time in vain.  At length, as Hildegarde’s strong fingers pressed hard on one spot of moulding, she felt it quiver.  There was a faint sound, like a murmur of protest; then slowly, unwillingly, the panel moved, obedient to the insistent fingers, and slid aside, revealing a square opening into—­the blackness of darkness.

“Oh, it’s a dungeon!” cried Gertrude, starting back.  “Perhaps the floor will give way, and let us down into places with knives and scythes.  You remember ‘The Dumberdene,’ Bell?”

“No fear, Gertrude,” said Hildegarde.  “Nothing more horrible than the dining-room is under our feet.  But this,—­this is very mysterious.  Can you see anything, Bell?”

“I begin to get a faint glimmer,” said Bell.  “Of course, if it is a chimney-room there cannot be any particular light.  Shall we creep in?  There is evidently a good deal of space.”