arine in a peaceful Scottish
loch! Then this was the secret base we had discussed. I looked up at
the wheel-house. In front of it was the very searchlight, with its
curious condenser that I had seen in the cavern.

What could it mean? I decided to slip overboard unseen, if possible,
swim to the shore, and get back over the rocks to the mouth of the
loch, and give the alarm if I should be fortunate enough to attract
the attention of any passing steamer.

But suddenly an idea struck me. I crept quickly up the ladder to the
deckhouse, threw my arms round the man at the wheel, flung him down on
to the deck, and swung the wheel round with all the strength I had in
me. There was a dull, crunching sound as the yacht lurched round. A
groaning shiver shook her, and, if I may be pardoned the illustration,
it felt exactly as if the ship were going to be sick. There were
hoarse cries from the men, and as the _Fiona_ righted herself I looked
astern. There was a frothy, many-coloured effervescence of oil and
water.

The submarine had disappeared! The yacht was nearing the head of the
loch. It was now or never. I made a dash for the side, but Fuller was
before me. He tripped me up, and I fell heavily to the deck, bruising
myself badly and giving my head a terrible bump. I put up my arm in a
last feeble attempt to defend myself. Fuller's hands closed on my
throat and nearly choked the life out of me, and as I sank back,
struggling for breath, a loud cry rang out from Hilderman.

"Guernstein! Guernstein!" he yelled.

Fuller let me go and ran to Hilderman. I lifted myself on my elbow.
Somehow or other I would crawl to the side, and get away before he
came back to finish me, but as I looked out over the stern I was
rooted to the spot by the sight that met my eyes. Or was I deluding
myself with the fantastic delirium of a dying man? Not four hundred
yards away was a motor-boat. It was Hilderman's _Baltimore II._, and
in it were Myra, my poor Myra, and Garnesk and Angus, all wearing
motor-goggles. But, strangest of all, a British destroyer was puffing
serenely behind them. No, I must be dreaming. Garnesk had told me he
was sending glasses for Myra. He had mentioned his connection with the
naval authorities. This must be the nightmare of death-agony.

Then Fuller rushed up the wheel-house ladder and jumped on to the
searchlight platform. Suddenly there flashed out on the grey light of
the dawn a vivid green ray. So, then, the mystery