felt more disposed to ascribe it
to a silly practical joke.

Eltham walked up briskly.

"You're in demand to-night, Doctor," he said. "A young person called
for you almost directly you had left your house, and, learning where you
were gone, followed you."

"Indeed!" I said, a trifle incredulously. "There are plenty of other
doctors if the case is an urgent one."

"She may have thought it would save time as you were actually up and
dressed," explained Eltham; "and the house is quite near to here, I
understand."

I looked at him a little blankly. Was this another effort of the unknown
jester?

"I have been fooled once," I said. "That 'phone call was a hoax--"

"But I feel certain," declared Eltham, earnestly, "that this is genuine!
The poor girl was dreadfully agitated; her master has broken his leg and
is lying helpless: number 280, Rectory Grove."

"Where is the girl?" I asked, sharply.

"She ran back directly she had given me her message."

"Was she a servant?"

"I should imagine so: French, I think. But she was so wrapped up I had
little more than a glimpse of her. I am sorry to hear that some one has
played a silly joke on you, but believe me--" he was very earnest--"this
is no jest. The poor girl could scarcely speak for sobs. She mistook me
for you, of course."

"Oh!" said I grimly, "well, I suppose I must go. Broken leg, you
said?--and my surgical bag, splints and so forth, are at home!"

"My dear Petrie!" cried Eltham, in his enthusiastic way--"you no doubt
can do something to alleviate the poor man's suffering immediately. I
will run back to your rooms for the bag and rejoin you at 280, Rectory
Grove."

"It's awfully good of you, Eltham--"

He held up his hand.

"The call of suffering humanity, Petrie, is one which I may no more
refuse to hear than you."

I made no further protest after that, for his point of view was evident
and his determination adamant, but told him where he would find the
bag and once more set out across the moonbright common, he pursuing a
westerly direction and I going east.

Some three hundred yards I had gone, I suppose, and my brain had been
very active the while, when something occurred to me which placed a new
complexion upon this second summons. I thought of the falsity of the
first, of the improbability of even the most hardened practical joker
practising his wiles at one o'clock in the morning. I thought of our
recent conversation; above all I thought of t