and in precisely the spot indicated, a slight, luminous spot
became dimly visible above the trees. The spot took uncertain form
high above the ghost-glow rising from the unseen stockade. For an
instant it hung suspended, pale-greenish, evanescent.

Then, as a faint plop! drifted to the watchers--a sound no louder
than a feeble clack of the tongue--this indefinite luminosity began to
sink, to fade, falling slowly, gradually dissipating itself in the dim
light over the stockade.

The Master nodded, smiling, with never any hint of praise or
approbation. The fulfilment of his order was to him no other than it
is to you, when you drop a pebble into water, to hear the splash of
it. That his plan should be working out, seemed to him a perfectly
obvious, inevitable thing. The only factor that could possibly have
astonished him, just now, would have been the nonappearance of that
slight, luminous cloudlet at the precise spot and moment designated.

Neither Bohannan, Alden, nor Rrisa was watching the slow descent of
the lethal gas. All three had their eyes fixed on their own lethal-gas
pistols and on their watches. At mathematically the correct second,
Bohannan discharged his piece, correctly sighting direction and
elevation.

As he pressed trigger, a light sighing eased itself from the slim
barrel. Something flicked through the leaves; and, almost on the
instant, the phenomenon of the little phosphorescent spot repeated
itself, though in a different place from the first one. Captain
Alden's and Rrisa's shots produced still other blurs of virescence.

Then, as they all waited, crouching, came another and another tiny
explosion, high aloft, at precisely ten-second intervals. Here, there,
they developed, until twenty-nine of these strange, bubble-like things
had burst above and all about the huge enclosure. Then darkness and
silence once more settled down.

Nothing seemed to have happened. Night still reigned, starry with
glimpses of sky through wind-swayed trees. One would have said
everything still remained precisely as it had been before.

Yet presently, within the stockade or near it, a certain uneasy
_melange_ of sounds began to develop. Here a cry became audible, there
a command. A startled voice called an order, but suddenly fell silent,
half-way through it. The worrying of the dog ceased with eloquent
suddenness. A curse died, unfinished.

And silence, as perfect as the silence of the unseen watchers strung
all ab