“Yes, the great yellow Mazarin stone. I’ve cast my net and I have my fish. But I have not got the stone. What is the use of taking them? We can make the world a better place by laying them by the heels. But that is not what I am out for. It’s the stone I want.”

“And is this Count Sylvius one of your fish?”

“Yes, and he’s a shark. He bites. The other is Sam Merton the boxer. Not a bad fellow, Sam, but the Count has used him. Sam’s not a shark. He is a great big silly bull-headed gudgeon. But he is flopping about in my net all the same.”

“Where is this Count Sylvius?”

“I’ve been at his very elbow all the morning. You‘ve seen me as an old lady, Watson. I was never more convincing. He actually picked up my parasol for me once. ‘By your leave, madame,’ said he — half-ltalian, you know, and with the Southern graces of manner when in the mood, but a devil incarnate in the other mood. Life is full of whimsical happenings, Watson.”

“It might have been tragedy.”

“Well, perhaps it might. I followed him to old Straubenzee’s workshop in the Minories. Straubenzee made the air-gun — a very pretty bit of work, as I understand, and I rather fancy it is in the opposite window at the present moment. Have you seen the dummy? Of course, Billy showed it to you. Well, it may get a bullet through its beautiful head at any moment. Ah, Billy, what is it?”

The boy had reappeared in the room with a card upon a tray. Holmes glanced at it with raised eyebrows and an amused smile.

“The man himself. I had hardly expected this. Grasp the nettle, Watson! A man of nerve. Possibly you have heard of his reputation as a shooter of big game. It would indeed be a triumphant ending to his excellent sporting record if he added me to his bag. This is a proof that he feels my toe very close behind his heel.”

“Send for the police.”

“I probably shall. But not just yet. Would you glance carefully out of the window, Watson, and see if anyone is hanging about in the street?”

Watson looked warily round the edge of the curtain.

“Yes, there is one rough fellow near the door.”

“That will be Sam Merton — the faithful but rather fatuous Sam. Where is this gentleman, Billy?”

“In the waiting-room, sir.”

“Show him up when I ring.”

“Yes, sir.”

“If I am not in the room, show him in all the same.”

“Yes, sir.”

Watson waited until the door was closed, and then he turned earnestly to his companion.

“Look here, Holmes, this is simply impossible. This is a desperate man, who sticks at nothing. He may have come to murder you.”

“I should not be surprised.”

“I insist upon staying with you.”

“You would be horribly in the way.”

“In his way?”

“No, my dear fellow — in my way.”