“But, good heavens!” cried the Duchess, almost in hysterics, “there aren’t any two-handed swords and battle-axes round here.”

Valentin was still busy with the paper in front of him.  “Tell me,” he said, still writing rapidly, “could it have been done with a long French cavalry sabre?”

A low knocking came at the door, which, for some unreasonable reason, curdled everyone’s blood like the knocking in Macbeth.  Amid that frozen silence Dr. Simon managed to say:  “A sabre—­ yes, I suppose it could.”

“Thank you,” said Valentin.  “Come in, Ivan.”

The confidential Ivan opened the door and ushered in Commandant Neil O’Brien, whom he had found at last pacing the garden again.

The Irish officer stood up disordered and defiant on the threshold.  “What do you want with me?” he cried.

“Please sit down,” said Valentin in pleasant, level tones.  “Why, you aren’t wearing your sword.  Where is it?”

“I left it on the library table,” said O’Brien, his brogue deepening in his disturbed mood.  “It was a nuisance, it was getting—­”

“Ivan,” said Valentin, “please go and get the Commandant’s sword from the library.”  Then, as the servant vanished, “Lord Galloway says he saw you leaving the garden just before he found the corpse.  What were you doing in the garden?”

The Commandant flung himself recklessly into a chair.  “Oh,” he cried in pure Irish, “admirin’ the moon.  Communing with Nature, me bhoy.”

A heavy silence sank and endured, and at the end of it came again that trivial and terrible knocking.  Ivan reappeared, carrying an empty steel scabbard.  “This is all I can find,” he said.

“Put it on the table,” said Valentin, without looking up.

There was an inhuman silence in the room, like that sea of inhuman silence round the dock of the condemned murderer.  The Duchess’s weak exclamations had long ago died away.  Lord Galloway’s swollen hatred was satisfied and even sobered.  The voice that came was quite unexpected.

“I think I can tell you,” cried Lady Margaret, in that clear, quivering voice with which a courageous woman speaks publicly.  “I can tell you what Mr. O’Brien was doing in the garden, since he is bound to silence.  He was asking me to marry him.  I refused; I said in my family circumstances I could give him nothing but my respect.  He was a little angry at that; he did not seem to think much of my respect.  I wonder,” she added, with rather a wan smile, “if he will care at all for it now.  For I offer it him now.  I will swear anywhere that he never did a thing like this.”

Lord Galloway had edged up to his daughter, and was intimidating her in what he imagined to be an undertone.  “Hold your tongue, Maggie,” he said in a thunderous whisper.  “Why should you shield the fellow?  Where’s his sword?  Where’s his confounded cavalry—­”

He stopped because of the singular stare with which his daughter was regarding him, a look that was indeed a lurid magnet for the whole group.