swiftly by the faint sound of a bump far
below.

Dropping "Who's Who" to the floor, Dundee flung open his living room
door and raced down three flights of stairs. He brought up, panting, at
the door of the basement. It was not locked and in another minute he was
standing before the big hot-air furnace. Above the fire box was a big
metal compartment--the reservoir for the heated air. And set into the
reservoir, to conduct the heat to the regions above, were three huge
pipes.

With strength augmented by excitement, Dundee tugged and tore at one of
the pipes until he had dislodged it. Then thrusting his hand into the
heat reservoir, he groped until he had found what he had known must be
there--_Judge Marshall's automatic, with the Maxim silencer screwed upon
the end of its short nose_.

At last he held in his hands the weapon with which Nita Leigh Selim and
Dexter Sprague had been murdered.

The ingeniousness of his own attempted murder moved him to such profound
admiration that he could scarcely feel resentment. If, in the excitement
of hunting for a promised clue, he had gone directly to the shelf,
standing in front of the hole in the register into which the end of the
silencer had been jammed, so that it showed scarcely at all, even to
eyes looking for it, he would now have been dead. And the gun and
silencer, after hurtling down the big hot-air pipe behind the register,
could have lain hidden for months, even years, in the heat reservoir of
the furnace.

With the weapon carefully wrapped in his handkerchief, Dundee went up
the stairs almost as swiftly as he had gone down them, meeting no one on
the way to his rooms on the top floor.

"My most heartfelt thanks to you, Cap'n!" he greeted his parrot. "If you
had not squawked last night and so frightened the murderer that he made
the vital error of covering your cage, I should never have annoyed you
again with my Sherlock ruminations on cases which do not interest you in
the slightest."

The parrot cackled hoarsely, but Dundee paid him scant attention. He
picked up the now harmless "Who's Who" and turned to page 410, a corner
of which had disappeared with the string that was still fastened to the
hair-trigger hammer of the Colt's .32. Very clever and very simple! The
murderer of two people and the would-be murderer of a third had had only
to unscrew the metal covering of the register, wedge the end of the
silencer into one of the many holes, replace the screws, an