of the gallery was a true oval, a geometrical ellipse, the
extraordinary acoustic properties of which I knew well. This peculiarly
shaped gallery contained two foci--one towards each end--and the nature
of the curve of the walls was such that sound issuing from either focus
was directed by reflection at various points to the other focus, and to
the other focus alone. Even across an enormous distance between such
would be the case. The swan's mouth was evidently at one focus; the
position of a man's head as he knelt at the altar would be without the
slightest doubt at the other. Could the pipe be used as a speaking-tube
when the water was turned off?

I felt so excited by this extraordinary discovery that it was only with
an effort that I maintained my self-control. I knew that presence of
mind was absolutely necessary in order to expose this horrible scheme. I
left the gallery and passed through the conservatory. Here I found the
gardener arranging some pots. I chatted to him for a few moments. He
looked surprised at seeing me up at such an unusual hour.

"Can you tell me how the fountain in the gallery is turned on or off?" I
asked.

"Yes, I can, sir," he replied; "the pipe runs along outside this stand,
and here's the tap."

I went across and looked at it. In the leaden pipe that was fastened to
the wall were two nuts, which could be turned by a small spanner, and
between them was a brass cap, which fitted on to a circular outlet from
the pipe.

"What is this used for?" I asked, pointing to the little outlet which
was closed by the cap.

"We screw the hose on there, sir, to water the flowers."

"I see," I answered; "so when you use the hose you shut off the water
from the fountain in the gallery."

"That's it, sir, and a wonderful deal of trouble it saves. Why it was
never done before I can't think."

"When was it done, then?" I asked. My heart was beating fast.

"It was Mr. Bagwell's thought, sir; he had it fixed on soon after he
came. He wanted to have plenty of water handy in order to water the
plants he brought back from India; but, lor! sir, they'll never live
through the winter, even under glass."

I waited to hear no more--the whole infernal plot was laid bare. The
second tap, which shut off the water both from the fountain and the hose
pipe, was, of course, quite useless, except for Bagwell's evil purpose.

I hurried straight up to Laurier's room. He was just preparing to rise.
His astonishment