and the next minute a tall figure, dimly
seen, came in his measured way along the gallery, as if to pass him,
while Leoni's hand slowly glided towards the hilt of his sword and
clutched it fast.

He held his breath and nerved himself for the cat-like leap he was
prepared to make as the sentinel came abreast, for he felt that it was
impossible that the man could pass him without his being seen.

But to the watcher's intense astonishment the sentry stopped short in
the centre of the gallery, when he was about a dozen yards away, turned
upon his heel, and began to retrace his steps. Leoni on the instant
judged that the man had come to the end of his beat, and if this were so
the task seemed easy, for by seizing the minute when his back was turned
and he was at the full extent of his monotonous tramp in the other
direction, it seemed to the doctor that it would be easy to step across
the gallery, raise the arras, and pass into the secret way.

"One at a time," muttered Leoni; "one at a time. Easy for us; but can I
make my chief piece obey me and move alone?"

The disposition was upon the watcher of the sentry to glide back at once
to where he had left Saint Simon and the King; but he felt that he must
make sure in this crisis of the adventure before he took his next step,
and he waited, closely pressed up against the tapestry, looking more
than ever like an embroidered figure, as the sentry halted far down the
gallery, softened by distance into a mere shadow, turned, and resumed
his pacing.

The task seemed harder than ever to stand pressed there against the
panelling, watching the coming of the stalwart guard, and it took all
the doctor's nerve and self-command to stand there so absolutely still
of body, while his nerves and thoughts were moving with an intensity
that literally thrilled.

"Coming towards his death," said Leoni mentally, as the man came on and
on, gradually ceasing to be so shadow-like and dim as he advanced. "His
life or mine. His life or mine. His life or mine," something within
him seemed to keep on saying, till the end of the sentry's beat appeared
to be quite over-passed and he was coming nearer, so near that Leoni
felt he saw him at last and the crisis was there, when the man stopped,
hesitated for a moment, then began pacing back just as before--but not
quite, for almost as soon as his back was turned Leoni's command over
his nerves and muscles ceased, and he began to glide silently along