achinery?--and doesn't. That's a battery, by all that's good! Now, what
the dickens does that battery do, I'd like to know?... 'A whirring
sound'--'hum-hum-hum!' That's how they described it to me this morning,
do you remember? Gad! And this is the thing that produced that
supernatural sound, then! Just a touch of a switch somewhere, and the
thing sets in motion. Now let's follow this wiring along to its
destination, and that will tell us a good deal."

He traced the line of palish flexible wire--so nearly the colour of the
old wood as to be hardly discernible unless one really knew of its
presence, round the wheel, and down on to the floor--the thing stood a
mere matter of inches from the window-sill--and then disappeared up
through a narrow piece of oak-coloured woodwork which was entirely
unnoticed from the panelling it covered, until it reached the
window-ledge and ended at the extreme right-hand corner of the middle
window, and vanished in a cluster of ivy which clung about the outside
of it, sending its tendrils right up to the edge of the sill itself.

Mr. Narkom followed the thing with fascination, poking a finger here and
there to help discern its threadlike and imperceptible progress, and was
almost as quick as Cleek in leaping out through the low sill to the
flower-bed below upon which those tell-tale footprints had made such a
strong impression. Then, of a sudden, they both stopped and stared
blankly at each other. For the end of the thing lay beneath the ivy
covering, in a little home-made switch which, touched by the finger,
obviously set the whole contraption in motion.

Cleek hopped back into the room to see that no one was about, but the
constable in charge stood outside the door, not in it, and they had
closed that door carefully behind them upon entrance. Then he leaned out
over the top of the window-sill and spoke softly to Mr. Narkom.

"Put your finger upon the switch when I say 'Go,'" he said in a tense
whisper, "and I'll stay inside here and watch how the thing works. Now
then.... _Go!_"

Mr. Narkom applied his finger forthwith, while to Cleek within came a
soft whirring, drumming sound, and then--an almost imperceptible "click"
and--the most amazing of all these amazing matters came instantly to
pass! For as he leapt out of the path of it, led by some mysterious,
intuitive impulse, a bullet sped rapidly past his ear, and lodged itself
in the woodwork, just a fraction of an inch below the spot