“Signed,” he said, folding the paper up deliberately, “Ekaterina Nevsky.”

It was as if a cable had snapped and a weight had fallen.  Revalenko sprang up and grasped Kazanovitch by the hand.  “Forgive me, comrade, for ever suspecting you,” he cried.

“And forgive me for suspecting you,” replied Kazanovitch, “but how did you come to shadow Kharkoff?”

“I ordered him to follow Kharkoff secretly and protect him,” explained Saratovsky.

Olga and Ekaterina faced each other fiercely.  Olga was trembling with emotion.  Nevsky stood coldly, defiantly.  If ever there was a consummate actress it was she, who had put the bomb at her own door and had rushed off to start Kennedy on a blind trail.

“You traitress,” cried Olga passionately, forgetting all in her outraged love.  “You won his affections from me by your false beauty—­yet all the time you would have killed him like a dog for the Czar’s gold.  At last you are unmasked—­you Azeff in skirts.  False friend—­you would have killed us all—­Saratovsky, Kharkoff—­ "

“Be still, little fool,” exclaimed Nevsky contemptuously.  “The spirilla fever has affected your brains.  Bah!  I will not stay with those who are so ready to suspect an old comrade on the mere word of a charlatan.  Boris Kazanovitch, do you stand there silent and let this insult be heaped upon me?”

For answer, Kazanovitch deliberately turned his back on his lover of a moment ago and crossed the room.  “Olga,” he pleaded, “I have been a fool.  Some day I may be worthy of your love.  Fever or not, I must beg your forgiveness.”

With a cry of delight the actress flung her arms about Boris, as he imprinted a penitent kiss on her warm lips.

“Simpleton,” hissed Nevsky with curling lips.  “Now you, too, will die.”

“One moment, Ekaterina Nevsky,” interposed Kennedy, as he picked up some vacuum tubes full of a golden-yellow powder, that lay on the table.  “The spirilla, as scientists now know, belong to the same family as those which cause what we call, euphemistically, the ‘black plague.’  It is the same species as that of the African sleeping sickness and the Philippine yaws.  Last year a famous doctor whose photograph I see in the next room, Dr. Ehrlich of Frankfort, discovered a cure for all these diseases.  It will rid the blood of your victims of the Asiatic relapsing fever germs in forty-eight hours.  In these tubes I have the now famous salvarsan.”

With a piercing shriek of rage at seeing her deadly work so quickly and completely undone, Nevsky flung herself into the little laboratory behind her and bolted the door.

Her face still wore the same cold, contemptuous smile, as Kennedy gently withdrew a sharp scalpel from her breast.

“Perhaps it is best this way, after all,” he said simply.

IV

THE FIREBUG