“You old fool!” she said in a low voice without pretence of piety, “what do you suppose you are trying to prove?  I tell you this man was innocent while with me.  But if he wasn’t innocent, he was still with me.  If he murdered a man in the garden, who was it who must have seen—­who must at least have known?  Do you hate Neil so much as to put your own daughter—­”

Lady Galloway screamed.  Everyone else sat tingling at the touch of those satanic tragedies that have been between lovers before now.  They saw the proud, white face of the Scotch aristocrat and her lover, the Irish adventurer, like old portraits in a dark house.  The long silence was full of formless historical memories of murdered husbands and poisonous paramours.

In the centre of this morbid silence an innocent voice said:  “Was it a very long cigar?”

The change of thought was so sharp that they had to look round to see who had spoken.

“I mean,” said little Father Brown, from the corner of the room, “I mean that cigar Mr. Brayne is finishing.  It seems nearly as long as a walking-stick.”

Despite the irrelevance there was assent as well as irritation in Valentin’s face as he lifted his head.

“Quite right,” he remarked sharply.  “Ivan, go and see about Mr. Brayne again, and bring him here at once.”

The instant the factotum had closed the door, Valentin addressed the girl with an entirely new earnestness.

“Lady Margaret,” he said, “we all feel, I am sure, both gratitude and admiration for your act in rising above your lower dignity and explaining the Commandant’s conduct.  But there is a hiatus still.  Lord Galloway, I understand, met you passing from the study to the drawing-room, and it was only some minutes afterwards that he found the garden and the Commandant still walking there.”

“You have to remember,” replied Margaret, with a faint irony in her voice, “that I had just refused him, so we should scarcely have come back arm in arm.  He is a gentleman, anyhow; and he loitered behind—­and so got charged with murder.”

“In those few moments,” said Valentin gravely, “he might really—­”

The knock came again, and Ivan put in his scarred face.

“Beg pardon, sir,” he said, “but Mr. Brayne has left the house.”

“Left!” cried Valentin, and rose for the first time to his feet.

“Gone.  Scooted.  Evaporated,” replied Ivan in humorous French.  “His hat and coat are gone, too, and I’ll tell you something to cap it all.  I ran outside the house to find any traces of him, and I found one, and a big trace, too.”

“What do you mean?” asked Valentin.

“I’ll show you,” said his servant, and reappeared with a flashing naked cavalry sabre, streaked with blood about the point and edge.  Everyone in the room eyed it as if it were a thunderbolt; but the experienced Ivan went on quite quietly: 

“I found this,” he said, “flung among the bushes fifty yards up the road to Paris.  In other words, I found it just where your respectable Mr. Brayne threw it when he ran away.”