He broke off abruptly.  He looked towards Arnold.  He was breathing heavily.  His sudden fit of passion had brought an unwholesome flush of color to his cheeks.

“Why should I stop?” Sabatini proceeded, mercilessly.  “Let me remind you of my sister’s presence.  Your lack of self-control is inexcusable.  One would imagine that you had committed some evil deed, that you were indeed an offender against the law.”

Again there was that tense silence.  Starling looked around him with the helpless air of a trapped animal.  Arnold sat there, listening and watching, completely fascinated.  There was something which made him shiver about the imperturbability, not only of Sabatini himself, but of the woman who sat by his side.

Sabatini poured himself out a glass of wine deliberately.

“Who in the world,” he demanded, “save a few unwholesome sentimentalists, would consider the killing of Rosario a crime?”

Starling staggered to his feet.  His cheeks now were ashen.

“You are mad!” he cried, pointing to Arnold.

“Not in the least,” Sabatini proceeded calmly.  “I am not accusing you of having killed Rosario.  In any case, it would have been a perfectly reasonable and even commendable deed.  One can scarcely understand your agitation.  If you are really accused of having been concerned in that little contretemps, why, here is our friend Mr. Arnold Chetwode, who was present.  No doubt he will be able to give evidence in your favor.”

Arnold was speechless for a moment.  Sabatini’s manner was incomprehensible.  He spoke as one who alludes to some trivial happening.  Yet even his light words could not keep the shadow of tragedy from the room.  Even at that instant Arnold seemed suddenly to see the flash of a hand through the glass-topped door, to hear the hoarse cry of the stricken man.

“I saw nothing but the man’s hand!” he muttered, in a voice which he would scarcely have recognized as his own.  “I saw his hand and his arm only.  He wore a red signet ring.”

Sabatini inclined his head in an interested manner.

“A singular coincidence,” he remarked, pleasantly.  “My sister has already told me of your observation.  It certainly is a point in favor of our friend Starling.  It sounds like the badge of some secret society, and not even the most ardent romanticist would suspect our friend Starling here of belonging to anything of the sort.”

Starling had resumed his luncheon, and was making a great effort at a show of indifference.  Nevertheless, he watched Arnold uneasily.

“Say, there’s no sense in talking like this!” he muttered.  “Mr. Chetwode here will think you’re in earnest.”

“There is, on the contrary, a very great deal of sound common sense,” Sabatini asserted, gently, “in all that I have said.  I want our young friend, Mr. Chetwode, to be a valued witness for the defense when the misguided gentlemen from Scotland Yard choose to lay a hand upon your shoulder.  One should always be prepared, my friend, for possibilities.  You great—­”