sly to doubt if this stream whereon we floated,
whose waters plashed and tinkled about us, were the Thames, the Tigris,
or the Styx.

The punt touched a bank.

"You will hear a clock strike in a few minutes," said the girl, with
her soft, charming accent, "but I rely upon your honor not to remove
the handkerchiefs until then. You owe me this."

"We do!" said Smith fervently.

I heard him scrambling to the bank, and a moment later a soft hand was
placed in mine, and I, too, was guided on to terra firma. Arrived on
the bank, I still held the girl's hand, drawing her towards me.

"You must not go back," I whispered. "We will take care of you. You
must not return to that place."

"Let me go!" she said. "When, once, I asked you to take me from him,
you spoke of police protection; that was your answer, police
protection! You would let them lock me up--imprison me--and make me
betray him! For what? For what?" She wrenched herself free. "How
little you understand me. Never mind. Perhaps one day you will know!
Until the clock strikes!"

She was gone. I heard the creak of the punt, the drip of the water
from the pole. Fainter it grew, and fainter.

"What is her secret?" muttered Smith, beside me. "Why does she cling
to that monster?"

The distant sound died away entirely. A clock began to strike; it
struck the half-hour. In an instant my handkerchief was off, and so was
Smith's. We stood upon a towing-path. Away to the left the moon shone
upon the towers and battlements of an ancient fortress.

It was Windsor Castle.

"Half-past ten," cried Smith. "Two hours to save Graham Guthrie!"

We had exactly fourteen minutes in which to catch the last train to
Waterloo; and we caught it. But I sank into a corner of the
compartment in a state bordering upon collapse. Neither of us, I
think, could have managed another twenty yards. With a lesser stake
than a human life at issue, I doubt if we should have attempted that
dash to Windsor station.

"Due at Waterloo at eleven-fifty-one," panted Smith. "That gives us
thirty-nine minutes to get to the other side of the river and reach his
hotel."

"Where in Heaven's name is that house situated? Did we come up or down
stream?"

"I couldn't determine. But at any rate, it stands close to the
riverside. It should be merely a question of time to identify it. I
shall set Scotland Yard to work immediately; but I am hoping for
nothing. Our escape will warn him