Balcom and Paul, however, were slower in going, and paced the hallway in earnest conversation.  Once they came to a dead halt close to the stairway leading down to the Graveyard of Genius.  They listened intently.  Evidently they came to a decision on something, for they left the house very hurriedly.

Immediately Locke called for the runabout.  Eva came running down-stairs and in a moment they took up the trail of the Balcom car.

It seemed as if they traveled for miles, and Locke was commencing to think that it was merely a wild-goose chase, when Balcom’s car came to a halt in one of the lower quarters of the city, before a house that was apparently tenantless.

To avoid discovery, Locke backed his car around a corner, got out, and watched their movements from a safe distance.

He saw Balcom, senior, alight, but Paul did not leave the car.  Locke was in some quandary what to do.  To attempt to enter the house without Paul’s seeing him and raising the alarm would, he realized, be impossible.  Therefore he waited for nearly half an hour before his patience was rewarded by seeing Balcom come out of the house, jump into the car, and drive off hurriedly with Paul.

Locke walked to the house and looked closely over the exterior.  It was little different from others in the same street.  Then he walked thoughtfully back to Eva and they argued pro and con about the advisability of attempting to enter.

Locke insisted on entering alone, but Eva would not hear of it.  Therefore, it was decided that they would go in together.

When Balcom had alighted from his car half an hour before he had merely stood for a moment in front of the door of the house when, mysteriously, the door had opened.

There was no one in sight.  But he was so familiar with the house that it might have been his own.  He descended a flight of stairs and stood before another door, where the same door-opening process was repeated.

Balcom entered a darkened room and for a moment seemed quite alone.  Then from out the shadows, with a little half run, half lope, a strange figure of man came toward him.

He was in reality large of frame, but stooped and bent with age.  An old frock-coat was wrapped about him.  But the most remarkable things about the man were a pair of weirdly fascinating eyes with a mad glint in them and an enormous full beard, snow white, that fell almost to his waist.

At times the man talked rationally, in fact with the forcefulness of a great savant.  Then, abruptly, he would leave off and the rest of his conversation was that of a babbling child.  He was seldom at rest, scampering here and there, not unlike a bird-dog on a fresh scent.  Seeking—­always seeking—­what?

Balcom grasped his arm in order to arrest his attention.

“Doctor Q,” he addressed him, “you can have the revenge you have sought so long.  Have you prepared everything?”