As I sat there, stunned by the blow, and turning the whole matter over in my mind, I was startled by the remarkable behaviour of the man sitting opposite me.
So far I had not paid much attention to him.
He was a thin, dark man of middle age, sallow of complexion, with a small pointed beard.
He had sat down opposite me so quietly that I had hardly noticed his arrival.
But his actions now were decidedly peculiar, to say the least of them.
Leaning forward, he deliberately helped me to salt, putting it in four little heaps round the edge of my plate.
"You will excuse me," he said, in a melancholy voice. "To help a stranger to salt is to help them to sorrow, they say.
That may be an unavoidable necessity.
I hope not, though.
I hope that you will be reasonable."
Then, with a certain significance, he repeated his operations with the salt on his own plate.
The symbol 4 was too plain to be missed.
I looked at him searchingly.
In no way that I could see did he resemble young Templeton, or James the footman, or any other of the various personalities we had come across. Nevertheless, I was convinced that I had to do with no less than the redoubtable Number Four himself.
In his voice there was certainly a faint resemblance to the buttoned-up stranger who had called upon us in Paris.
I looked round, undecided as to my course of action.
Reading my thoughts, he smiled and gently shook his head.
"I should not advise it," he remarked. "Remember what came of your hasty action in Paris.
Let me assure you that my way of retreat is well assured.
Your ideas are inclined to be a little crude. Captain Hastings, if I may say so."
"You devil," I said, choking with rage, "you incarnate devil!"
"Heated - just a trifle heated.
Your late lamented friend would have told you that a man who keeps calm has always a great advantage."
"You dare to speak of him," I cried. "The man you murdered so foully.
And you come here -" He interrupted me.
"I came here for an excellent and peaceful purpose.
To advise you to return at once to South America.
If you do so, that is the end of the matter as far as the Big Four are concerned.
You and yours will not be molested in any way.
I give you my word as to that."
I laughed scornfully.
"And if I refuse to obey your autocratic command?"
"It is hardly a command.
Shall we say that it is - a warning?" There was a cold menace in his tone. "The first warning," he said softly. "You will be well advised not to disregard it."
Then, before I had any hint of his intention, he rose and slipped quickly away towards the door.
I sprang to my feet and was after him in a second, but by bad luck I cannoned straight into an enormously fat man who blocked the way between me and the next table.
By the time I had disentangled myself, my quarry was just passing through the doorway, and the next delay was from a waiter carrying a huge pile of plates who crashed into me without the least warning.
By the time I got to the door there was no sign of the thin man with the dark beard.
The waiter was fulsome in apologies, the fat man was sitting placidly at a table ordering his lunch. There was nothing to show that both occurrences had not been a pure accident.
Nevertheless, I had my own opinion as to that.
I knew well enough that the agents of the Big Four were everywhere.
Needless to say, I paid no heed to the warning given me.
I would do or die in the good cause.
I received in all only two answers to the advertisements.
Neither of them gave me any information of value.
They were both from actors who had played with Claud Darrell at one time or another.
Neither of them knew him at all intimately, and no new light was thrown upon the problem of his identity and present whereabouts.
No further sign came from the Big Four until about ten days later.
I was crossing Hyde Park, lost in thought, when a voice, rich with a persuasive foreign inflection, hailed me.
"Captain Hastings, is it not?"