that it will record the slamming of a cellar
door across the street. No one can go up those stairs next door without
letting me know it, no matter how cautious he is about it."

Craig stood there some minutes holding the thing over his ears and
listening intently.

"The vibrodyne machine isn't running," he remarked finally after
repeated adjustments of the geophone. "But someone is in that little
room under Creighton's workshop. I suspected that something was down
there after that watch crystal test of mine. Now I know it. I wonder
what the man is doing?"

There was no excuse yet, however, for breaking into the room on the
other side of the wall and under Creighton's. Kennedy went out and
watched. Though we waited some time nobody came out. He went back to our
own room in the rear of the first floor. Though we both listened some
time, neither of us could now hear a sound through the geophone except
those made by passing trolleys and street vehicles.

Inquiry about the neighborhood did not develop who was the tenant or
what was his business. In fact the results were just the reverse. No one
seemed to know even the business conducted there. The room back of the
locked door which Miss Laidlaw had passed was shrouded in mystery.

Nothing at all of any value was being recorded by the geophone when
Kennedy glanced quickly at his watch. "If we are to see Miss Laidlaw and
meet that Mrs. Barry, we had better be on our way," he remarked
hurriedly.

Miss Laidlaw was living in a handsome apartment on Central Park, West.
We entered and gave our cards to the man at the door of her suite, who
bowed us into a little reception room. We entered and waited.

Suddenly we were aware that someone in the next room, a library, was
talking. Whether we would or not we could not help overhearing what was
said. Apparently two women were there, and they were not taking care how
loud they spoke.

"Then you object to my even knowing Mr. Creighton?" asked one of the
voices, pausing evidently for a reply which the other did not choose to
make. "I suppose if it was Mr. Tresham you'd object, too."

There was something "catty" and taunting about the voice. It was a hard
voice, the voice of a woman who had seen much, and felt fully capable of
taking care of herself in more.

"You can't make up your mind which one you care for most, then? Is that
it?" pursued the same voice. "Well, I'll be a sport. I'll leave you
Creighton--if you can keep him."