to send
from his office one of his assistants to cover the Sowell Street houses.
He cast a last, reluctant look at the closed blinds, and moved away. As
he did so, two itinerant musicians dragging behind them a small street
piano on wheels turned the corner, and, as the rain had now ceased, one
of them pulled the oil-cloth covering from the instrument and,
seating himself on a camp-stool at the curb, opened the piano. After
a discouraged glance at the darkened windows, the other, in a hoarse,
strident tenor, to the accompaniment of the piano, began to sing. The
voice of the man was raucous, penetrating. It would have reached the
recesses of a tomb.

"She sells sea-shells on the sea-shore," the vocalist wailed. "The
shells she sells are sea-shells, I'm sure."

The effect was instantaneous. A window was flung open, and an indignant
householder with one hand frantically waved the musicians away, and with
the other threw them a copper coin.

At the same moment Ford walked quickly to the piano and laid a
half-crown on top of it.

"Follow me to Harley Street," he commanded. "Don't hurry. Take your
time. I want you to help me in a sort of practical joke. It's worth a
sovereign to you."

He passed on quickly. When he glanced behind him, he saw the two men,
fearful lest the promised fortune might escape them, pursuing him at a
trot. At Harley Street they halted, breathless.

"How long," Ford demanded of the one who played the piano, "will it take
you to learn the accompaniment to a new song?"

"While you're whistling it," answered the man eagerly.

"And I'm as quick at a tune as him," assured the other anxiously. "I can
sing----"

"You cannot," interrupted Ford. "I'm going to do the singing myself.
Where is there a public-house near here where we can hire a back room,
and rehearse?"

Half an hour later, Ford and the piano-player entered Sowell Street
dragging the piano behind them. The amateur detective still wore his
rain-coat, but his hat he had exchanged for a cap, and, instead of a
collar, he had knotted around his bare neck a dirty kerchief. At the
end of the street they halted, and in some embarrassment Ford raised his
voice in the chorus of a song well known in the music-halls. It was a
very good voice, much too good for "open-air work," as his companion
had already assured him, but, what was of chief importance to Ford, it
carried as far as he wished it to go. Already in Wimpole Street four
coins of the rea