ear was Inspector John Weymouth. How, having escaped
death in the Thames, he had crossed London unobserved, we never knew;
but his trick of knocking upon his own door at half-past two each
morning (a sort of dawning of sanity mysteriously linked with old
custom) will be a familiar class of symptom to all students of
alienation.

I revert to the night when Smith solved the mystery of the knocking.

In a car which he had in waiting at the end of the village we sped
through the deserted streets to New Inn Court. I, who had followed
Nayland Smith through the failures and successes of his mission, knew
that to-night he had surpassed himself; had justified the confidence
placed in him by the highest authorities.

We were admitted to an untidy room--that of a student, a traveler and a
crank--by a plain-clothes officer. Amid picturesque and disordered
fragments of a hundred ages, in a great carven chair placed before a
towering statue of the Buddha, sat a hand-cuffed man. His white hair
and beard were patriarchal; his pose had great dignity. But his
expression was entirely masked by the smoked glasses which he wore.

Two other detectives were guarding the prisoner.

"We arrested Professor Jenner Monde as he came in, sir," reported the
man who had opened the door. "He has made no statement. I hope there
isn't a mistake."

"I hope not," rapped Smith.

He strode across the room. He was consumed by a fever of excitement.
Almost savagely, he tore away the beard, tore off the snowy wig dashed
the smoked glasses upon the floor.

A great, high brow was revealed, and green, malignant eyes, which fixed
themselves upon him with an expression I never can forget.

IT WAS DR. FU-MANCHU!

One intense moment of silence ensued--of silence which seemed to throb.
Then:

"What have you done with Professor Monde?" demanded Smith.

Dr. Fu-Manchu showed his even, yellow teeth in the singularly evil
smile which I knew so well. A manacled prisoner he sat as unruffled as
a judge upon the bench. In truth and in justice I am compelled to say
that Fu-Manchu was absolutely fearless.

"He has been detained in China," he replied, in smooth, sibilant
tones--"by affairs of great urgency. His well-known personality and
ungregarious habits have served me well, here!"

Smith, I could see, was undetermined how to act; he stood tugging at
his ear and glancing from the impassive Chinaman to the wondering
detectives.

"What are we to do,