THAT night in London the Chief of the Criminal Investigation Department sat in his office. It required ten minutes to midnight, and he had just laid down his pen after several hours’ hard work over official correspondence and reports.

The Goldberg case was still exercising the public mind, and several editors were asking the world from editorial easy chairs what the police were paid for.

The night was warm, and through the open window came vague and fugitive sounds from the city that never sleeps; voices, the bells of passing hansoms and the clop, clop of the horses’ hoofs, the hum of distant traffic.

A little draught of wind suddenly stirred the papers on the desk before him; he turned, the door was open, and Freyberger stood before him, pale, haggard and bearing a black bag in his hand. Behind Freyberger stood a stranger.

“I knocked, sir,” said Freyberger.

“Ah! I was thinking. I suppose I did not hear you. Sit down—this gentleman——?”

“This gentleman’s name is Hellier, sir,” replied Freyberger. “I have ventured to bring him with me as he has assisted me in clearing up the Gyde case.”

“Ah! what’s that you say?”

“The Gyde case, sir. Also he has saved my life to-day—”

“Sit down, sit down,” said the chief, indicating chairs. “This is good, if it is as you say. I want details; but first tell me, is Sir Anthony Gyde alive?”

“No, sir, he was murdered in the Cottage on the Fells.”

“Good God! by whom?”

“Klein.”

“Is Klein alive?”

“No, sir, he is dead. He died to-day, and his body lies in the mortuary at Reading. Let me say at once, and with the humility of a man who has just escaped a terrible death, that all my assumptions were absolutely correct. Klein, alias Kolbecker, alias Müller, was the author of the Lefarge tragedy, the Gyde tragedy and all the subsidiary murders, concluding with the murder of Bronson yesterday. Look at this.”

He produced a black notebook from his pocket. The chief examined the book; it was a volume of some hundred pages or so, every page covered with close writing.

“This book,” said Freyberger, taking back the volume, “contains the life history of the greatest criminal who ever lived. It is the diary of Ludwig Spahn, alias Müller, alias Kolbecker, alias Klein. I mastered it in the train to-night, and from it I will sketch you the story of which the murder of Sir Anthony Gyde is but a chapter.

“Spahn was born in Munich, sixty-five years ago.”

“Sixty-five?”

“Yes, sir. He was an old man.”

“But the man in the photograph was a man of middle age.”

“Yes, sir. He seemed of middle age, but I will explain the matter as I go on. Spahn, at seventeen, left the business to which he was apprenticed and went to Rome to study art, or, to speak more correctly, to teach it, for this strange genius had ideals of his own, and very soon he had a little following, a cult. Vicious to the core, he never could keep money. He was always in debt. One day he murdered a banker, was caught red-handed, sentenced to death and allowed to escape the extreme penalty by that infernal law which allows murderers to escape unexterminated. He was condemned to imprisonment for life and released after twenty-five years.

“He was fifty when he left prison, full of hatred towards society and a determination to be revenged.

“He went to Paris.

“The art which was born with him remained with him, and the love of pleasure.

“He refused to be old, and, with the aid of the art of the chemist and the maker-up, he appeared to the world as a man at least twenty years younger than he was.

“He lived for years in Paris in the Latin Quarter, a notoriously vicious character, yet forgiven for the sake of his genius. His sculptures were marvellous, but his vice and laziness were to match, so he made little profit of his art and did little work.

“His hatred of the rich and well-to-do amounted to a monomania, and he was always searching around for some means by which he might avenge himself upon them.

“To the man who hates a class, an individual of that class will serve as a butt for his revenge.

“One day, walking along a street in Paris, he saw coming towards him what seemed a little old man wearing a pinafore. It was a child wearing a mask.

“The occurrence gave him food for thought. ‘If,’ said he to himself, ‘a man who makes these paper masks for five sous a dozen, can produce an even momentary illusion, what could not a genius do in the same direction were he to give all his mind to the matter?’

“He played with the subject in his mind.

“‘If I wanted to make the mask of a man,’ thought he, ‘a mask that would deceive everybody by its resemblance to the flesh, how would I proceed?

“‘I would first have to procure a cast of his face, or execute a bust of him exactly identical with the reality. Only very slightly larger.

“‘I would then rub that face of marble with a very fine powder, and I would apply a coating of the finest caoutchouc, over that a layer of stiffening varnish.

“‘I would remove the whole, and paint the interior of the caoutchouc with the flesh tints, thus giving the true appearance of life, for the human face is painted from the inside.

“‘I would then back the thing with a thicker layer of rubber and remove the stiffening varnish from the outside.

“‘If my art did not fail me, I would now have a facsimile of my friend or my enemy’s face. Could I wear it and masquerade as him? Only on two conditions (1) that I could make the inside of the mask a perfect mould of my own face (2) that he was a man, a man of my own height and a man who wore glasses and a beard, for the joining at the eyes and at the neck would present an insuperable difficulty were I to imitate a clean-shaven man who did not wear glasses.’

“He brooded over the thing.

“One day he fell in with M. Lefarge, a rich jeweller, who was at times a frequenter of the Latin Quarter, and the whole diabolical plan of the Lefarge case was conceived in a flash.

“The plan of robbing and murdering a rich man in such a manner that the world would fancy that the rich man was the assassin, not the victim.

“He made a bust of Lefarge, from the bust he made Lefarge’s face. Lefarge wore a beard and glasses. The making of the exterior of the mask was a bagatelle; the real difficulty was the interior, which had to be a perfect adaptation to his own features, but he did it.

“Whilst this was going o............