The question to be solved was this:  Why did Capella and his wife quarrel in the first instance?  Perhaps, that way, light might come.

He asked a footman if Mrs. Capella would receive him.  The man glanced at his card.

“Yes, sir,” he said at once.  “Madam gave instructions that if either you or Mr. David called you were to be taken to her boudoir, where she awaits you.”

The room was evidently on the first floor, for the servant led him up the magnificent oak staircase that climbed two sides of the reception hall.

But this was fated to be a day of interruptions.  The barrister, when he reached the landing, was confronted by the Italian.

“A word with you, Mr. Brett,” was the stiff greeting given to him.

“Certainly.  But I am going to Mrs. Capella’s room.”

“She can wait.  She does not know you are here.  James, remain outside until Mr. Brett returns.  Then conduct him to your mistress.”

Capella’s tone admitted of no argument, nor was it necessary to protest.  Brett always liked people to talk in the way they deemed best suited to their own interests.  Without any expostulation, therefore, he followed his limping host into a luxuriously furnished dressing-room.

Capella closed the door, and placed himself gently on a couch.

“Does your friend fight?” he said, fixing his dark eyes, blazing with anger, intently on the other.

“That is a matter on which your opinion would probably be more valuable than mine.”

“Spare me your wit.  You know well what I mean.  Will he meet me on the Continent and settle our quarrel like a gentleman, not like a hired bravo?”

“What quarrel?”

“Mr. Brett, you are not so stupid.  David Hume, notwithstanding his past, may still be deemed a man of honour in some respects.  He treated me grossly this morning.  Will he fight me, or must I treat him as a cur?”

Brett, without invitation, seated himself.  He produced a cigarette and lit it, adding greatly to Capella’s irritation by his provoking calmness.

“Really,” he said at last, “you amuse me.”

“Silence!” he cried imperatively, when the Italian would have broken out into a torrent of expostulations.  “Listen to me, you vain fool!”

This method of address had the rare merit of achieving its object.  Capella was reduced to a condition of speechless rage.

“You consider yourself the aggrieved person, I suppose,” went on the Englishman, subsiding into a state of contemptuous placidity.  “You neglect your wife, make love to an honourable and pure-minded girl, stoop to the use of unworthy taunts and even criminal innuendos, lose such control of your passion as to lay sacrilegious hands upon Helen Layton, and yet you resent the well-merited punishment administered to you by her affianced husband.  Were I a surgeon, Mr. Capella, I might take an anatomical interest in your brain.  As it is, I regard you as a psychological study in latter-day blackguardism.  Do you understand me?”