At last he turned to me and said, "Walter, here is a ghost caught
in the act."

I looked dubiously at the irregular up-and-down scrawl on the
paper, while he rang up the Homicide Bureau of the Central Office
and left word for O'Connor to call him up the first thing in the
morning.

Still eyeing with satisfaction the record traced on the sheets of
paper, he lighted a cigarette in a matter-of-fact way and added:
"It proves to be a very much flesh-and-blood ghost, this 'John.'
It walked up to the wall back of that cabinet, rapped, listened
to old Vandam, rapped some more, got the answer it wanted, and
walked deliberately away. The cabinet, as you may have noticed,
is in a corner of the room with one side along the hallway. The
ghost must have been in the hall."

"But who was it?"

"Not so fast, Walter," laughed Craig. "Isn't it enough for one
night that we have found out that much?"

Fortunately I was tired, or I certainly should have dreamed of
rappings and of "John" that night. I was awakened early by
Kennedy talking with someone over the telephone. It was Inspector
O'Connor.

Of course I heard only one side of the conversation, but as near
as I could gather Kennedy was asking the inspector to obtain
several samples of ink for him. I had not heard the first part of