"Go out into the road and look at the fanlight," Bell directed.

David complied eagerly. A sharp cry of surprise escaped him as he looked
up. The change was apparent. Instead of the figures 218 he could read now
the change to 219--a fairly indifferent 9, but one that would have passed
muster without criticism by ninety-nine people out of a hundred. With a
strong light behind the figures the clumsy 9 would never have been
noticed at all. The very simplicity and ingeniousness of the scheme was
its safeguard.

"I should like to have the address of the man who thought that out,"
David said, drily.

"Yes, I fancy that you are dealing with quite clever people," Bell
replied. "And now I have shown you how utterly you have been deceived
over the number we will go a little farther. For the present, the way in
which the furniture trick was worked must remain a mystery. But there has
been furniture here, or this room and the hall would not have been so
carefully swept and garnished whilst the rest of the house remains in so
dirty a condition. If my eyes don't deceive me I can see two fresh nails
driven into the archway leading to the back hall. On those nails hung the
curtain that prevented you seeing more than was necessary. Are you still
incredulous as to the house where you had your remarkable adventure?"

"I confess that my faith has been seriously shaken," David admitted. "But
about the furniture? And about my telephone call from Mr. Gates's town
house? And about my adventure taking place in the very next house to the
one taken by him at Brighton? And about Miss Gates's agitation when she
learnt my identity? Do you call them coincidences?"