But the last word was scarcely audible, for he collapsed across the table.  I stood there aghast.  Howell, suddenly noticing me, told me roughly to clear out, as I was not wanted.  I demanded to know what had happened, but I was told that it did not concern me.  My idea was that Mr. Henfrey had been drugged, for he was still alive and apparently dazed.  I afterwards heard, however, that Howell had pressed the needle of a hypodermic syringe containing a newly discovered and untraceable poison which he had obtained in secret from a certain chemist in Frankfort, who makes a speciality of such things.”

“And what happened then?” asked Hugh, aghast and astounded at the story.

“Benton and Howell sent me out of the room.  They waited for over an hour.  Then Howell went down to the car.  Afterwards, when all was clear, they half carried poor Mr. Henfrey downstairs, placed him in the car, and drove away.  Next day I heard that my guest had been found by a constable in a doorway in Albemarle Street.  The officer, who first thought he was intoxicated, later took him to St. George’s Hospital, where he died.  Afterwards a scratch was found on the palm of his hand, and the doctors believed it had been caused by a pin infected with some poison.  The truth was, however, that his hand was scratched in opening a bottle of champagne at supper.  The doctors never suspected the tiny puncture in the hair at the nape of the neck, and they never discovered it.”

“I knew nothing of the affair,” declared The Sparrow, his face clouded by anger.  “Then Howell was the actual murderer?”

“He was,” Yvonne replied.  “I saw him press the needle into Mr. Henfrey’s neck, while Benton stood by, ready to seize the victim if he resisted.  Benton and Howell had agreed to kill Mr. Henfrey, compel his son to marry Louise, and then get Hugh out of the world by one or other of their devilish schemes.  Ah!” she sighed, looking sadly before her.  “I see it all now—­everything.”

“Then it was arranged that after I had married Louise I should also meet with an unexpected end?”

“Yes.  One that should discredit you in the eyes of your wife and your own friends—­an end probably like your father’s.  A secret visit to London, and a mysterious death,” Mademoiselle replied.

She spoke quite calmly and rationally.  The shock of suddenly encountering the two persons who had been uppermost in her thoughts before those terrible injuries to her brain had balanced it again.  Though the pains in her head were excruciating, as she explained, yet she could now think, and she remembered all the bitterness of the past.

“You, M’sieur Henfrey, are the son of my dead friend.  You have been the victim of a great and dastardly conspiracy,” she said.  “But I ask your forgiveness, for I assure you that when I invited your father up from Woodthorpe I had no idea whatever of what those assassins intended.”

“Benton is already under arrest for another affair,” broke in The Sparrow quietly.  “I heard so from London yesterday.”