which we had to answer. There is only one
possible way. You are aware that the Underground runs clear of tunnels
at some points in the West End. I had a vague memory that as I have
travelled by it I have occasionally seen windows just above my head.
Now, suppose that a train halted under such a window, would there be
any difficulty in laying a body upon the roof?"

"It seems most improbable."

"We must fall back upon the old axiom that when all other contingencies
fail, whatever remains, however improbable, must be the truth. Here
all other contingencies HAVE failed. When I found that the leading
international agent, who had just left London, lived in a row of houses
which abutted upon the Underground, I was so pleased that you were a
little astonished at my sudden frivolity."

"Oh, that was it, was it?"

"Yes, that was it. Mr. Hugo Oberstein, of 13 Caulfield Gardens, had
become my objective. I began my operations at Gloucester Road Station,
where a very helpful official walked with me along the track and
allowed me to satisfy myself not only that the back-stair windows of
Caulfield Gardens open on the line but the even more essential fact
that, owing to the intersection of one of the larger railways, the
Underground trains are frequently held motionless for some minutes at
that very spot."

"Splendid, Holmes! You have got it!"

"So far--so far, Watson. We advance, but the goal is afar. Well,
having seen the back of Caulfield Gardens, I visited the front and
satisfied myself that the bird was indeed flown. It is a considerable
house, unfurnished, so far as I could judge, in the upper rooms.
Oberstein lived there with a single valet, who was probably a
confederate entirely in his confidence. We must bear in mind that
Oberstein has gone to the Continent to dispose of his booty, but not
with any idea of flight; for he had no reason to fear a warrant, and
the idea of an amateur domiciliary visit would certainly never occur to
him. Yet that is precisely what we are about to make."

"Could we not get a warrant and legalize it?"

"Hardly on the evidence."

"What can we hope to do?"

"We cannot tell what correspondence may be there."

"I don't like it, Holmes."

"My dear fellow, you shall keep watch in the street. I'll do the
criminal part. It's not a time to stick at trifles. Think of
Mycroft's note, of the Admiralty, the Cabinet, the exalted person who
waits for news. We are bound to go."

M