"who let those fellows in? Are you a wizard?"

Craig smiled coolly as the ventilation cleared the room of the
deadly cyanogen.

"On the window-sill outside is a selenium cell. Selenium is a bad
conductor of electricity in the dark, and an excellent conductor
when exposed to light. I merely moved my coat and hat, and the
light from the furnace which was going to suffocate us played
through the glass on the cell, the circuit was completed without
your suspecting that I could communicate with friends outside, a
bell was rung on the street, and here they are. Andrews, there is
the murderer of Morowitch, and there in his hands are the
Morowitch--"

Poissan had moved toward the furnace. With a quick motion he
seized the long tongs. There was a cloud of choking vapour.
Kennedy leaped to the switch and shut off the current. With the
tongs he lifted out a shapeless piece of valueless black
graphite.

"All that is left of the priceless Morowitch jewels," he
exclaimed ruefully. "But we have the murderer."

"And to-morrow a certified check for one hundred thousand dollars
goes to Mrs. Morowitch with my humblest apologies and sympathy,"
added Andrews. "Professor Kennedy, you have earned your
retainer."