timid knock on the door of my room.

"'Watson,' said I, 'here comes some one for advice. Do you wish to wager a
small bottle upon it?'

"'Yes,' he answered, with a smile. 'I am thirsty and I'd like a small
bottle; and while I do not expect to win, I'll take the bet. I should like
to know, though, how you know.'

"'It is quite simple,' said I. 'The timidity of the knock shows that my
visitor is one of two classes of persons--an autograph-hunter or a client,
one of the two. You see I give you a chance to win. It may be an
autograph-hunter, but I think it is a client. If it were a creditor, he
would knock boldly, even ostentatiously; if it were the maid, she would
not knock at all; if it were the hall-boy, he would not come until I had
rung five times for him. None of these things has occurred; the knock is
the half-hearted knock which betokens either that the person who knocked
is in trouble, or is uncertain as to his reception. I am willing, however,
considering the heat and my desire to quench my thirst, to wager that it
is a client.'

"'Done,' said Watson; and I immediately remarked, 'Come in.'

"The door opened, and a man of about thirty-five years of age, in a
bathing-suit, entered the room, and I saw at a glance what had happened.

"'Your name is Burgess,' I said. 'You came here from London this morning,
expecting to return to-night. You brought no luggage with you. After
luncheon you went in bathing. You had machine No. 35, and when you came
out of the water you found that No. 35 had disappeared, with your clothes