ke this," said McCarthy, as we came at
last into the receiving room for accident cases, "you get some idea,
Brett, of the size of this great London machine working about us. You
might walk about the streets for a week and never see a serious
accident, or even an accident at all, and yet, you see, here they come
all day long--a stream of people damaged or killed in the machine."

A decent workman was having a gashed hand dressed and strapped, and a
navvy with bandages about his head was being led away by a friend.
Nurses and dressers were waiting ready to take their orderly turns at
the incoming casualties, and as we looked a more serious case was
brought in on an ambulance by two policemen. The patient was a ragged,
disreputable-looking fellow of middle age, in grimy and tattered
clothes, whose head had been roughly bandaged by the policemen who
brought him. He had been knocked down and kicked on the head by a
butcher's cart-horse, it seemed, in Moorgate Street, and he was quite
insensible. A very short examination showed that the case was nothing
trivial, and McCarthy sent me to sit in his private room to wait lunch,
while he gave the matter his personal attention.

When he returned he brought a small crumpled envelope in his hand. "That
case is put to bed," he said, "still insensible."

"Is it very bad?" I asked.

"Slight fracture of the occipital, and, of course, concussion of the
brain--probably contusion, too, I expect we shall find presently. Not so
over serious for a healthy man, but I'm afraid he's an old soaker--the
sort that crumple up at a touch. Nobody knows him, and there's nothing
to identify him in the pockets--a few coppers, an old knife, and so on.
So we can't send to tell his friends--unless we bring in your friend
Martin Hewitt to trace 'em out, which would come too expensive.
Besides," McCarthy added, dropping into a seat before his desk, "if he's
got any friends they'll come, sooner or later, when they miss him. This
is the only thing he'd got beside what's in the pockets--he'd been sent
on a message, probably."

My friend held up the crumpled envelope and took from it a small key.
"He'd got this envelope gripped tightly in his hand," he said, "but
there was no address on it, so we tore it open in the hope of finding
one inside. But there was nothing there but the key. If you were a very
promising pupil of your friend Hewitt, I should expect you to take a
glance at it and tell us the man's addr