four-room suite
just a few days before. This suite was on the fifteenth floor, just half
way up in the big structure.

They went to the manager of the building and frankly stated their
suspicions. "We want to enter that suite when the tenant is not there,"
they explained, "and we want him forestalled from entering while we are
examining the premises."

"Hadn't we better notify the police?" asked the building manager, who
had broken out in a sweat when he heard the dire disaster which might be
in store for the stately Acme building.

"Not yet," said Linane. "You see, we are not sure: we have just been
putting two and two together."

"We'll get the building detective, anyway," insisted the manager.

"Let him come along, but do not let him know until we are sure. If we
are right we will find a most unusual infernal machine," said Linane.

* * * * *

The three men entered the suite with a pass-key. The detective was left
outside in the hall to halt anyone who might disturb the searchers. It
was as Jenks had thought. In an inner room they found a diabolical
machine--a single string stretched across two bridges, one of brass and
one of wood. A big horsehair bow attached to a shaft operated by a motor
was automatically sawing across the string. The note resulting was
evidently higher than the range of the human ear, because no audible
sound resulted. It was later estimated that the destructive note was
several octaves higher than the highest note on a piano.

The entire machine was enclosed in a heavy wire-net cage, securely
bolted to the floor. Neither the string or bow could be reached. It was
evidently the Mad Musician's idea that the devilish contrivance should
not be reached by hands other than his own.

How long the infernal machine had been operating no one knew, but the
visitors were startled when the building suddenly began to sway
perceptibly. Jenks jumped forward to stop the machine but could not find
a switch.

"See if the machine plugs in anywhere in a wall socket!" he shouted to
Linane, who promptly began examining the walls. Jenks shouted to the
building manager to phone the police to clear the streets around the big
building.

"Tell the police that the Acme Theater building may crash at any
moment," he instructed.

The engineers were perfectly cool in face of the great peril, but the
building manager lost his head completely and began to run around in
circles mutt