Finally Brent leaned over and spoke in a whisper, looking about as though the very walls might have ears.

“My dear fellow,” he confided, “for some time I have been considering your water-motor.  I will return the model to you—­release the patent to the world.”

He drew back to watch the effect on the aged inventor.  Could it be that Brent was lying?  Or was it fear?  Could it be that at last his seared conscience was troubling him?

At that exact moment, up-stairs, in a private laboratory in the house, sat a young man at a desk—­a handsome, strong-faced, clean-cut chap.  All about him were the scientific instruments which he used to test inventions offered to Brent.

A look of intent eagerness passed over his face.  For Quentin Locke was not testing any of Brent’s patents just now.  Over his head he had the receivers of a dictagraph.

It was a strange act for one so recently employed as manager of Brent’s private laboratory.  Yet such a man must have had his reasons.

One who was interested might have followed the wire from the dictagraph-box in the top drawer of the desk down the leg of the desk, through the very walls to the huge chandelier in the library below, where, in the ornamented brass-work, reposed a small black disk about the size of a watch.  It was the receiving-end of the dictagraph.

Suddenly the young man’s face broke out into a smile and without thinking he stopped writing what the little mechanical eavesdropper was conveying him from below.  He listened intently as he heard a silvery laugh over the wire.

“Oh, I didn’t know you were busy.  I thought these flowers—­Well, never mind.  I’ll leave them, anyway.”

It was Eva Brent, daughter of the head of the firm, who had danced in from the conservatory like a June zephyr in December.

“My dear,” Locke could hear the patent magnate welcome, “it is all right.  Stay a moment and talk to this gentleman while I go down to the museum.”

Locke listened eagerly, glancing now and then at a photograph of Eva Brent on his own desk, while she chatted gaily with the inventor.  It was evident that Eva had not the faintest idea of the hard nature of the business of her father.

Meanwhile, Brent himself had left the library and passed through the portiered door into the hall.  He did not turn up the grand staircase in the center of the wide hall, but hurried, preoccupied, to a door under the stairs that opened down to the cellar.

He started to open it to pass down.  As he did so he did not hear a light footstep on the stairs as his secretary, Zita Dane, came down.  But he did not escape her watchful eye.

“Mr. Brent,” she called, “is there anything I can do?”

Brent paused.  “Wait a moment for me in the library,” he directed, as he turned again to enter the cellar.

He closed the door and Zita watched him with an almost uncanny interest, then turned to the library to join Eva and the new-comer.