Neither of us could accept the fact for a moment; we stood there,
looking from the dead man to the tortured man who only swooned, in a
state of helpless incredulity.

Then the explanation flashed upon us both, simultaneously, and with a
cry of baffled rage Smith leaped along the passage to the second door.
It was wide open. I stood at his elbow when he swept its emptiness
with the ray of his pocket-lamp.

There was a speaking-tube fixed between the two rooms!

Smith literally ground his teeth.

"Yet, Petrie," he said, "we have learnt something. Fu-Manchu had
evidently promised Eltham his life if he would divulge the name of his
correspondent. He meant to keep his word; it is a sidelight on his
character."

"How so?"

"Eltham has never seen Dr. Fu-Manchu, but Eltham knows certain parts
of China better than you know the Strand. Probably, if he saw
Fu-Manchu, he would recognize him for who he really is, and this, it
seems, the Doctor is anxious to avoid."

We ran back to where we had left Karamaneh.

The room was empty!