excited questions. We raced up the stairs. Repeated

rings and knocks brought no reply, but listening closely I could distinguish a hollow groan coming from within.

The hall porter proved to have a master key, and after

a few difficulties he consented to use it.

Poirot went straight to the inner room. A whiff of

chloroform met us. On the floor was Sonia Daviloff,

gagged and bound, with a great wad of saturated cotton

wool over her nose and mouth. Poirot tore it off and

began to take measures to restore her. Presently a doctor arrived, and Poirot handed her over to his charge

and drew aside with me. There was no sign of Dr.

Savaronoff.

"What does it all mean?" I asked, bewildered.

"It means that before two equal deductions I chose

the wrong one. You heard me say that it would be easy

for any one to impersonate Sonia Daviloff because her

uncle had not seen her for so many years?"

"Yes?"

"Well, precisely the opposite held good also. It was equally easy for any one to impersonate the uncle.''

"What?"

"Savaronoff did die at the outbreak of the Revolution. The man who pretended to have escaped with such

terrible hardships, the man so changed 'that his own

friends could hardly recognise him,' the man who successfully laid claim to an enormous fortune--"

"Yes. Who was he?"

"Number Four. No wonder he was frightened when

Sonia let him know she had overheard one of his private

conversations about the 'Big Four.' Again he has

slipped through my fingers. He guessed I should get on

the right track in the end, so he sent off the honest Ivan on a tortuous wild goose chase, chloroformed the girl,

and got out, having by now doubtless realised most of

the securities left by Madame Gospoja."

"But--but who tried to kill him then?"

"Nobody tried to kill him. Wilson was the intended

victim all along."

"But why?"

"My friend, Savaronoff was the second greatest chess player in the world. In all probability Number Four did

not even known the rudiments of the game. Certainly he

could not sustain the fiction of a match. He tried all he knew to avoid the contest. When that failed, Wilson's

doom was sealed. At all costs he must be prevented

from discovering that the great Savaronoff did not even

know how to play chess. Wilson was fond of the Ruy

Lopez opening, and was certain to use it. Number Four

arranged for death to come with the third move, before

any complications of defence set in."

"But, my dear Poirot," I persisted, "are we dealing with a lunatic? I quite follow your reasoning, and admit that you must be right, but to kill a man just to sustain his role! Surely there were simpler ways out of the difficulty than that? He could have said that his doctor forbade

the strain of a match."

Poirot wrinkled his forehead.

"Cerfainement, Hastings," he said, "there were other ways, but none so convincing. Besides, you are