"Probably not. 'Rigel Four' would be an utterly meaningless thought to anyone ignorant of Rigel; and, except when making a conscious effort, as in directing strangers, I never think of its location in terms of galactic co-ordinates. I suppose that the location of a home planet is always taken for granted. That would seem to leave us just about where we were before in our search for 'X,' except for your implied ability to intercept another of his thoughts, almost at will. Explain, please." "Not _my_ ability--ours." Camilla smiled, confidently. "I couldn't do it alone, neither could you, but between us I don't believe that it will be too difficult. You, with your utterly calm, utterly unshakable certainty, can drive a thought to any corner of the universe. You can fix and hold it steady on any indicated atom. I can't do that, or anything like it, but with my present ability to detect and to analyze, I am not afraid of missing 'X' if we can come within parsecs of him. So my idea is a sort of piggy-back hunting trip; you to take me for a ride, mentally, very much as Worsel takes Con, physically. That would work, don't you think?" "Perfectly, I am sure." The stolid Rigellian was immensely pleased. "Link your mind with mine, then, and we will set out. If you have no better plan of action mapped out, I would suggest starting at the point where we lost him and working outward, covering an expanding sphere." "You know best. I will stick to you wherever you go. I am ready." * * * * * Tregonsee launched his thought; a thought which, at a velocity not to be measured even in multiples of that of light, generated the surface of a continuously enlarging sphere of space. And with that thought, a very part of it, sped Camilla's incomprehensibly delicate, instantaneously reactive detector web. The Rigellian, with his unhuman perseverance, would have surveyed total space had it been necessary; and the now adult Camilla would have stayed with him. However, the patient pair did not have to comb all of space. In a matter of hours the girl's almost infinitely tenuous detector touched, with infinitesimal power and for an inappreciable instant of time, the exact thought-structure to which it had been so carefully attuned. "Halt!" she flashed, and Tregonsee's mighty superdreadnought shot away along the indicated line at maximum blast. "You are not now thinking at him, of course, but how sure are you that he did not feel your detector?" Tregonsee asked.