"Careful, Dora," he admonished. "There's a small gas-bomb inside."

The five now conferred a bit and it was agreed that this time the inquisitive Mr. Locke would surely trouble them no more.

"With Locke out of the way," promised Paul to Dora, "the road to our fortune is clear."

A moment later Paul left the apartment, descended in the elevator, and jumped into a taxicab and was off.

Locke from his cab had, of course, seen all this, had seen Paul and Dora on the balcony and the departure. But he knew nothing of the three men who had gone to the same apartment.

He waited until Paul passed out of sight, then stepped out of his cab, making a careful calculation as to the exact location of the woman's apartment, for he had determined to find out about her. From the hall boy he learned that it was De Luxe Dora, of whom he knew, and it was only a matter of seconds when he was admitted.

Dora swept over graciously toward him.

"Will you answer me one question?" he asked, in answer to a query from her.

She nodded assent.

"How long have you known Mr. Balcom's son?"

"He is an old friend," she replied. "I'm expecting him to return at any moment. Won't you be seated? Please excuse me just a moment."

Before Locke could say a word she had left the room. Left alone himself, Locke took in all the details of the room and again and again his eye wandered to a Louis XIV desk.

Feeling certain that this woman was without doubt connected in some way with the plots, he felt justified in opening the desk to obtain evidence. He tiptoed over to it and tried to open it. It stuck at first, but after one or two silent, well-directed blows which he so well knew how to administer the sliding panel stood unlocked.

He glanced around. There was no one to be seen. He moved back the panel.

There was a flash and a tiny puff of smoke. Locke coughed once, clutched at his throat, and lay gasping on the floor.

Immediately the three men rushed out, carrying ropes and holding handkerchiefs to their nostrils. One ran to the window and threw it wide open, admitting gusts of air to clear away the fumes. The others began to bind Locke as De Luxe Dora appeared in the doorway and calmly directed operations.

On the roof of the apartment several moments later in the just-gathering dusk five figures might have been seen. Three men and a woman were conferring, while at their feet was a man tightly bound and unconscious.

In the background was a huge water-tank, with a ladder leading to its brim.

Suddenly the conspirators straightened up. They had come to a decision.

The three men lifted the unconscious figure and bore it up the ladder.

The tank was empty. One of the men jumped down into it, while the others lowered their victim after him. Then they passed down ropes.

There were two spouts at the bottom of the tank through which water was pumped. Also there were pipes running upward. To these pipes they tied Locke. Then the men climbed out and, as their last fiendish act, turned the water on.

With a sneer Dora turned and led the way down-stairs again.

"They'll find his body when they have to clean the tank again," she exclaimed.

At Brent Rock, during the absence of Locke, Eva had donned her street clothes, since it was nearing the hour of eight when she and Locke were due to be at the inventor's workshop to render the restitution. She went down-stairs and asked the butler about Locke. But the man replied that Mr. Locke had not yet returned.

Eva was very uneasy by this time, and, thinking to save time, was about to go down to the Graveyard of Genius to get the models of the two inventions, when Zita came down the hall carrying a fair sized package which she tried hard to conceal. Eva greeted her and continued down to the cellar, as Zita, with a sort of grim smile, left the house.

Eva came to the great door, pushed the secret spring, and in a moment was inside the gloomy place. She went directly to the spot where the two inventions had been kept. They were gone.

Alarmed, she rushed up-stairs.

Still Locke did not return. Nor did any word come from him. It was now very near to eight. Eva decided to go, for surely Locke would be there.

When Zita arrived at the inventor's, in her hands was still the mysterious package. She carried it gingerly, then raised it to her ear.

From within it there came a faint ticking sound. What was it inside?

She looked at her wrist-watch. It was still some minutes before eight.

She knocked at the inventor's door.

The inventor at once admitted her. It was a neat little workshop in which every detail had been thought out with care--the home, one might say, of a methodical workman.

The inventor manifested some surprise at seeing Zita, but politely asked her to enter, and offered her a chair. Zita declined and plainly showed her nervousness.

"Will you please give this package to Mr. Locke and Miss Brent when they come at eight?" she asked.

Winters agreed and accepted the package, looking quizzically at her as he did so, just as he had earlier in the day.

Zita, unable to control her curiosity, burst out with the question uppermost on her mind.

"Why do you look at me in such a strange manner?" she queried.

The inventor merely turned his gaze away and shrugged.

"Mr Balcom tells me that you know the secret of my birth," pressed Zita.

The inventor looked up quickly. "Who did Mr. Balcom say you were?" he asked.

"He told me that I was Brent's daughter," replied Zita, keenly watching the aged face.

"Balcom lied to you," hastened the inventor.

Already there was a ponderous tread on the stairs, but Winters did not seem to notice it.

"You are not Brent's daughter," he pursued, more slowly.

The door opened swiftly and an emissary stood framed there, a knife poised in his hand. Behind him stood the Automaton.

"You are--"

At that instant the inventor caught sight of the intruders. With a look of horror in his eyes he threw out his hands to protect himself, but he was too late. The knife whizzed through the air and a second later pierced his throat. He fell to the floor--dead.

At the moment when the emissary, followed by the Automaton, entered, Zita, watching her chance, managed to escape from the room, stumbled, and almost half-fell down the stairs.

Already, in the huge water-tank that stood on the roof of the apartment of Dora, Locke had revived as he felt the water and had found himself already half submerged, with the water rapidly pouring in. At first he could not grasp his terrible predicament, but before long the full horror of it burst on him and he struggled madly to free himself. Since his body was stretched at full length, it was impossible to use the ordinary tricks of which he was master. His arms were bound, and he well knew that to release one of them constituted his sole chance of escape.

He contracted his muscles and, inch by inch, he worked his right arm free. By this time the water had risen until he was fairly beneath its surface. Could he last long enough to free himself?

He worked frantically. Finally, with his lungs almost bursting, he managed to free the other arm, then the rope that bound his neck. To release his feet was, to him, child's play, and he stood up.