Nor were his fears unfounded. He had barely passed the fountain where, half an hour before, he had been set free, when an emissary came out from behind a neighboring tree and took up his trail.

De Luxe Dora also had waited only long enough to see Eva and Locke enter Brent Rock, when she turned her runabout around and drove rapidly back to Professor Hadwell's. She arrived there just in time to meet an automobile coming from the opposite direction and containing three emissaries of the Automaton.

In answer to an inquiry, Dora pointed out the chemist's house to them.

They piled out, and their leader knocked at the door, while Dora drove off.

The chemist answered, and the leader produced a vial, glibly lying as he handed it over.

"The Williams Drug Company sent me to have this stuff analyzed," said the leader. "I'll wait."

As the professor admitted him he did not see the other two men pressed close to the wall on either side of the door. The moment the professor's back was turned they slinked after their leader into the house. In a dark corner of the hallway they crouched as their leader went into the laboratory with the chemist.

The professor sniffed at the vial, which contained nothing but pure water, and in surprise turned to the emissary for an explanation. But it was too late. The emissary dealt him a blow with a blunt instrument that stunned him and, as he reeled back and grasped at a table, the other thugs rushed from the hall and rained blow after blow on his venerable head and beat him to the floor. A convulsive shudder--a long-drawn-out sigh--and he lay still.

With barely a glance at him the emissaries set to work to smash all the paraphernalia of the place, sparing nothing in order to make sure that the antidote would be destroyed. Glass tubes, retorts, bottles, even furniture were smashed to bits in their orgy of ruin--and there, in the midst of the debris, his life's work finished, lay the old chemist, dead.

Tiring of their own efforts, the murderers at last desisted. One of them went to the street door and peered out, but in a moment was back with the others.

"Quick--that fellow Locke is coming."

He was right. Locke had immediately quit Brent Rock and had come directly to the chemist's in the hope of forestalling any further attempt by Flint to inveigle Eva into dealing with him.

The door had been left ajar and, although he thought it strange, Locke was without suspicion and entered the hallway. He called to his old friend, but the dead lips could not answer and the emissaries would not.

Greatly alarmed now, Locke strode to the laboratory. For a moment he stood as though petrified as the horrid scene burst upon his vision. He ran to the chemist and knelt beside his battered body.

With a rush the emissaries darted from their hiding-place and were upon him.

Although taken unawares, Locke was, in a measure, ready for them. One he grabbed in a clever jiu-jitsu hold and sent him hurtling through the air to crash in a heap in a far corner of the room. Leaping to his feet, he beat another to the floor. The third villain was of tougher fiber. Up and down the laboratory they battled, stumbling over broken furniture, now falling to the floor, where they rolled over and over, first one, then the other gaining the mastery, while the broken glass with which the floor was littered cut their clothing to ribbons and bit into their flesh.

Locke was slowly gaining the upper hand when the thug whom he had thrown over his head recovered. The brute took the situation in at a glance, saw his pal in trouble, and, sneaking treacherously behind Locke, dealt him a terrific blow with the butt of a revolver. Locke dropped to the floor as if pole-axed and lay still.

One of the thugs kicked him as he lay defenseless, and then, spying a row of coat-hooks in an inner hallway, with fiendish ingenuity directed the others who had joined him. They strung Locke up by his thumbs so that he hung, half suspended, with his toes just off the floor.

As one of them searched him Locke was still unconscious. They found nothing but a few bank-notes and the automatic revolver that Locke always carried.

Slowly Locke regained his senses. The agony of his strained thumbs was almost unbearable. But he was not the man to give up.

By this time two of the emissaries had gone, leaving one, who seated himself quite close to Locke, where he was examining the revolver. With the stoicism of an Indian, Locke manfully tried to evolve a plan by which he might escape. Like a flash it came to him, but it was a plan so fraught with the possibility of failure that he would not have decided on it except for the agony of the strain on his thumbs.

Directly opposite him and at a distance of four or five feet was a door leading to a back alley. This door the emissary now guarding him had locked as a precaution against surprise and had carefully placed the key in his vest pocket.

Locke weighed each detail of his plan and then, bracing his feet firmly against the wall, he suddenly shot his lower limbs forward and, like the closing of a pair of giant shears, he wrapped his legs about the neck of the emissary and immediately exerted enormous pressure with his knees.

The emissary, taken totally by surprise, struggled to break the hold, and Locke's thumbs were almost wrenched from their sockets. But he held on grimly. Soon the thug's struggles subsided, Locke released him, and he slipped to the floor.

Locke was wearing a low-cut shoe. Strange that a man's life may hinge on such a slight detail, but this fact enabled him to work off his right shoe and his sock. He extended his bare foot, and with his toes searched the pocket of the emissary for the key to the door. Finally he found it.

Locke held the key as firmly as he might between his toes and, projecting his body by a muscular effort far away from the wall, he managed to insert the key in the lock. He turned it. The door was unlocked now. A swift downward movement of his foot against the knob and the door swung open.

He braced himself against its edge and, with his back firmly pressed against the wall, relieved the strain on his thumbs. He rested a moment and then, as it were, walked up the edge of the door until his feet reached the top. Swinging one leg over the door, by patient effort he was enabled to release one swollen thumb, then the other. An instant later he dropped down and leaned exhaustedly against the wall.

While Locke was held in the room things had happened which would have set him nearly crazy with anxiety. Eva, having heard nothing from him, had become alarmed and had telephoned to the chemist. This was at quarter to five, and she had supposed that it was the chemist who answered her. In reality it had been an emissary, and he had told her that the final experiment to find an antidote for her father's malady had been really a failure and that Locke had left some time before.

After all that she had endured, this was almost the final blow to Eva.

She thought of Flint and Baker's dock and five o'clock. There was no time to lose if she were to save her father. So she pulled herself together, seized her hat and cloak, and started for the door.

Here Zita stopped her and offered to accompany her, but she declined.

She hastily asked the direction of Baker's dock from the butler, and then ran out of the house and sprang to the steering-wheel of her waiting car. With a whir of the starter she was away.

Flint had arrived at the dock long before and was now slinking in and out among the crates and boxes as he sought diligently for a safe hiding-place. But his nerves, none too strong at the best, were now running riot, and nowhere could he feel a sense of security so that he could remain quiet.

It was while he was sneaking from one pile of bales to another that an emissary hailed him.

"Are you Flint?" he demanded.

"Y-e-s," came quaveringly from Flint.

"Well, there's a lady in the office asking for you."

Such was the fascination of any of the emissaries of the Automaton over Flint by this time that he followed the man without question, particularly as he felt that he would be spared, since the lady in the office could be none other than Eva.

Together they walked toward the entrance and, with an order to wait, the emissary halted Flint close to a pile of crates and left him. Flint dared not move. A premonition of impending disaster must have come over him, for his knees shook and a clammy sweat broke out on his forehead.

Without sound a gigantic iron hand and arm protruded from behind a crate and, for a moment, hung suspended over Flint's head. Then, with a swift encircling movement, that hooklike arm wrapped itself around Flint's neck and drew him into the shadow. The mighty form drew the victim close--and it was over.

The Automaton picked up the body as though it had been a mere feather-weight and stalked out to the waiting emissaries. A trap-door was opened and Flint's body was dashed into the river. Thus it was that all his scheming came to an end and his secret from Madagascar, which he had told Brent, but which now lay locked in that mad-man's mind, was stilled with Flint's dead lips.

At the chemist's shop Locke was by this time recovering from the terrible ordeal through which he had passed. He bathed his swollen thumbs, and by rubbing them was able somewhat to restore the circulation. Then he stepped to the telephone and gave the Brent Rock number.

It was Zita who answered him.

"Eva has gone alone to Baker's dock," she answered to his inquiry, in half-triumphant jealousy.

Locke did not wait to hear more. There was not a moment to be lost. He rushed out, disheveled as he was, into the street, slamming the door after him. It seemed hours before he could find a taxicab.

"Baker's dock!" he yelled. "And twenty dollars if you make it in ten minutes."

He did not know that the emissaries had robbed him of everything, nor would it have made any difference, for he could easily have fixed it with the driver through his police and Secret Service connections.

In the mean time Eva's car had met with misfortune, and she had been compelled to stop. She jumped out and busied herself with a missing cylinder.

Locke's taxi was running smoothly and arrived at the dock well within the time he had ordered. Locke jumped out and started to pay. It was then that he discovered that he was without money. The driver became angry and hard to pacify with the story of the robbery, but Locke finally convinced him that all was right with the Department of Justice.

Locke walked through the gates to the dock and for a moment stood nonplussed. This dock had none of the turmoil and bustle naturally associated with docks when a steamer is about to leave.

He cautiously proceeded between the piles of merchandise toward the end of the wharf. Of one thing he was now certain and a prayer of relief came to his lips. He was there before Eva and able to guard her from any danger that might arise.