d the engineer took out a pocket-book and pencil. "I fear," he
proceeded, "that I am a little confused in my explanation--I am naturally
rather agitated. As you will see presently, my offices consist of three
rooms, two at one side of a corridor, and the other opposite--thus." He
made a rapid pencil sketch.

[Illustration]

"In the outer office my men usually work. In the inner office I work
myself. These rooms communicate, as you see, by a door. Our ordinary way
in and out of the place is by the door of the outer office leading into
the corridor, and we first pass through the usual lifting flap in the
barrier. The door leading from the _inner_ office to the corridor is
always kept locked on the inside, and I don't suppose I unlock it once in
three months. It has not been unlocked all the morning. The drawer in
which the missing drawings were kept, and in which I saw them at ten
o'clock this morning, is at the place marked D; it is a large chest of
shallow drawers in which the plans lie flat."

"I quite understand. Then there is the private room opposite. What of
that?"

"That is a sort of private sitting-room that I rarely use, except for
business interviews of a very private nature. When I said I never left my
office, I did not mean that I never stirred out of the inner office. I was
about in one room and another, both the outer and the inner offices, and
once I went into the private room for five minutes, but nobody came either
in or out of any of the rooms at that time, for the door of the private
room was wide open, and I was standing at the book-case (I had gone to
consult a book), just inside the door, with a full view of the doors
opposite. Indeed, Worsfold was at the door of the outer office most of the
short time. He came to ask me a question."

"Well," Hewitt replied, "it all comes to the simple first statement. You
know that nobody left the place or arrived, except the postman, who
couldn't get near the drawings, and yet the drawings went. Is this your
office?"

The cab had stopped before a large stone building. Mr. Dixon alighted and
led the way to the first-floor. Hewitt took a casual glance round each of
the three rooms. There was a sort of door in the frame of ground glass
over the barrier to admit of speech with visitors. This door Hewitt pushed
wide open, and left so.

He and the engineer went into the inner office. "Would you like to ask
Worsfold and Ritter any questions?" Mr. Dixon inquired.