Carefully Locke worked the umbrella steel and the string until he had caught the bolt.  Then he shot the bolt back and rose to his feet.  All watched him expectantly as he threw open the door.

Such a sight as met their eyes one could scarcely picture.

There were Brent and Flint at the table—­laughing—­laughing.  The candles had long since burned out.  On the floor lay the automaton model.

“Father!” cried Eva, running to him.

But there was no look of recognition on Brent’s face.

“Don’t you know me?  Speak to me!  Father!”

Instead, Brent merely patted her shoulder and laughed hollowly.  Eva, on her knees by him, sobbed and smoothed his head by turns.

Locke, bending over Flint, found him in much the same condition.

Meanwhile, Balcom and Paul had picked up the model of the automaton and exchanged a quick glance.

“This man Locke’s actions are suspicious,” exclaimed Balcom, hastily.  “He was in the house last night.”

Outside they could hear the arrival of the detectives summoned by the butler.

“Go to Eva,” nudged Balcom to Paul.

A moment later the butler entered with the detectives.

At the sight of the automaton model in Balcom’s hands the butler cried out: 

“That is what attacked me last night—­only larger—­much larger!”

All eyes were now on the butler.  Quickly Balcom took advantage of the situation thus created.  Locke, also, left Flint and moved over to the group examining the model.  As he did so his eye caught a piece of paper under the sideboard.  He was about to pick it up when he realized that all were looking at him.  Quickly he covered his discovery and faced them.

“This man is the stranger in the house,” cried Balcom, in anger.  “Arrest him and make him explain.”

It was the work of only an instant for the chief detective to step up to Locke and slip the bracelets on his wrists.

“Don’t!” cried Eva.

“Please—­my dear—­your father,” remonstrated Paul.

At that instant Brent was seized with another violent fit of coughing and laughter.  Eva, distracted, was half fainting.

Thus, with Locke handcuffed, Balcom and Paul were triumphant.

Locke saw his chance.  But the handcuffs prevented him from using his hands.  In the instant that all were diverted toward Brent, with incredible deftness Locke slipped his hand from the cuffs, one link of which fell open as if by magic, through a secret all his own.  He reached down and picked up the paper under the sideboard and read it.  It was the letter Brent had been writing and served only to increase his perplexity.  He read it again, then crushed it into his pocket, and before any one had discovered his trick had slipped his hand back into the cuffs and they were locked again.

At that very moment the telephone rang and the chief of the detectives answered.  As he did so a perplexed expression crossed his face and he walked over quickly to Locke.