g her--one thought was hammering away in her brain, and playing
havoc with her nerves. That thought was the inexplicable feeling within
her that there was something in connection with that hideous crime which
she ought to recollect, something which--if she could only remember what
it was--would give her the clue to the tragic mystery, and for once
ensure her triumph over this self-conceited and sarcastic scarecrow in
the corner.

He was watching her through his great bone-rimmed spectacles, and she
could see the knuckles of his bony hands, just above the top of the
table, fidgeting, fidgeting, fidgeting, till she wondered if there
existed another set of fingers in the world which could undo the knots
his lean ones made in that tiresome piece of string.

Then suddenly--_a propos_ of nothing, Polly _remembered_--the whole
thing stood before her, short and clear like a vivid flash of
lightning:--Mrs. Owen lying dead in the snow beside her open window; one
of them with a broken sash-line, tied up most scientifically with a
piece of string. She remembered the talk there had been at the time
about this improvised sash-line.

That was after young Greenhill had been discharged, and the question of
suicide had been voted an impossibility.

Polly remembered that in the illustrated papers photographs appeared of
this wonderfully knotted piece of string, so contrived that the weight
of the frame could but tighten the knots, and thus keep the window open.
She remembered that people deduced many things from that improvised
sash-line, chief among these deductions being that the murderer was a
sailor--so wonderful, so complicated, so numerous were the knots which
secured that window-frame.

But Polly knew better. In her mind's eye she saw those fingers, rendered
doubly nervous by the fearful cerebral excitement, grasping at first
mechanically, even thoughtlessly, a bit of twine with which to secure
the window; then the ruling habit strongest through all, the girl could
see it; the lean and ingenious fingers fidgeting, fidgeting with that
piece of string, tying knot after knot, more wonderful, more
complicated, than any she had yet witnessed.

"If I were you," she said, without daring to look into that corner
where he sat, "I would break myself of the habit of perpetually making
knots in a piece of string."

He did not reply, and at last Polly ventured to look up--the corner was
empty, and through the glass door beyond the desk,