Robert pondered a minute. Obviously the _Sphere_ offered the most promising avenue of escape; but how to gain access to it at night without arousing suspicion and probably fatal resistance was the question. A plan came to him. He could visit the _Sphere_ the following afternoon under some plausible excuse without exciting suspicion, and could remain tinkering in it, ostensibly to make some repairs. Unless disturbed, he could wait till dark, then cautiously bring it over to the garden. The scheme was simple enough, but the possibilities for failure were numerous. Should the emperor become suspicious and have the _Sphere_ watched, his plans would be of no avail. A dozen other possible obstacles occurred to him but no better plan. Swiftly he outlined it to Zola, obtaining her promise that she and her father would be in readiness to leave the following night. Her absolute confidence in his ability at once disturbed and inspired Robert. He felt that he must succeed at all costs. Here was probably his only chance of saving the maid of his dreams. He must not be found wanting. “Quick! The emperor!” said Modah, tensely, appearing suddenly, as from nowhere. Pressing the princess’ hand in hasty farewell, Robert followed Modah quickly. Down the long hallway they hurried. At a dark and forbidding doorway Modah halted and signaled Robert to follow. The next moment they had plunged into the darkness of a narrow passage leading off the main one. Groping blindly along the wall in the wake of Modah’s hurrying footsteps. Robert narrowly missed flattening his nose against the opposite wall as they turned a sharp bend. A moment later, however, a faint light glimmered ahead, revealing Modah scurrying along, a few yards in advance. A moment later Modah stopped. Together they listened for some sound of pursuit. But the silence of the massive, walled passage was unbroken save for their own bated breath. Once more they hurried ahead, and soon Robert recognized with relief the passage leading into their apartment. Both Taggert and the professor were eagerly awaiting him. Briefly Robert explained the result of his excursion, and suggested his plans for their escape with the princess and her father. It developed that Modah had taken a different and roundabout route back for greater safety, though the divers dim passages all had looked much alike to Robert. He was only certain that it had taken them longer to return. He resolved to substantially reward the vigilant Modah at the first opportunity. Had the emperor discovered him with the princess, all would have been lost. * * * * * Early in the morning Taggert left to examine the _Sphere_ and survey the ground for an escape. Ostensibly he went to obtain some needed articles of wearing apparel. Robert and the professor took the precaution to instruct him as to what articles they wanted at breakfast, while Modah and Numid were both present.