Though Lindsay and Cicely had satisfactorily accomplished their quest,
they felt there were many points in connection with their adventure at
the Manor that still puzzled them. The mystery surrounding the lantern
room had not yet been cleared up, neither had the strange behaviour of
Mrs. Wilson and Scott been accounted for.

So anxious were they to decide these perplexing points that they
determined to confide the whole affair to Monica, and see if she could
offer any explanation. A month ago it would have been impossible to get
her for half an hour to themselves, but since their finding of the
treasure the other girls were ready to allow them a special claim to her
society, and took it as a matter of course when they carried her off to
the summer house for a private chat.

Monica listened attentively to the story of their various experiences
and suspicions. At the end she laughed heartily, then suddenly looked
grave.

"You dear silly children!" she exclaimed. "It was a case of much ado
about nothing, and yet you nearly ran into such great danger that it
makes me shudder even to think about it. There certainly was a reason
for visiting the attic, though not at all of the kind you imagined. It
contains a large cistern, which supplies the water for the bath and the
kitchen boiler. This is fed by a tank on the roof that catches the rain,
and in dry weather it is apt to get out of order. If it is not working
properly, it makes a curious blowing noise."

"Like groaning?" asked Cicely.

"Yes, very like groaning, though it would need a gigantic prisoner to
utter such fearful moans of distress. No wonder you thought somebody was
being tortured!" and Monica laughed again.

"You can understand," she continued, "that with so many girls in the
house requiring baths, we were afraid lest the tank should run dry, and
were continually examining the cistern, to make sure that the water was
flowing properly. If it had stopped even for an hour, it might have
caused the kitchen boiler to burst."

"Did Mrs. Wilson go to look, then?" enquired Lindsay.

"Either Mrs. Wilson or Scott went every day. My mother was so anxious
about it that I several times ran up myself, so that I could tell her
all was perfectly safe. Mrs. Wilson was equally nervous. We had so
little rain in June that she was sure the tank must be nearly empty."

"Then that was what she and Scott meant about the noise and danger,
when they were talking in the picture g