Paul followed him and found Captain Harper in an observation room, writhing on a cot in a storm of tears and emotional fury. He beat against the walls and the floor with his fists as his sobbing continued beyond control. "What happened to him?" Paul demanded. "We have three others in the same condition," said Barker. "We tried to determine the effect of a pure feedback impulse, and fed it back to each of them in amplified form as we found it on their charts. This is what happened. I'm afraid we may have cost them their sanity, and we don't know why." "How could their own feedback do such a thing to them?" he asked in wonder. "What part of the chart did you take it from?" "We used the impulse that didn't get through, the one that was blocked so that error resulted. Apparently this is the alternative to error." He nodded toward the writhing, sobbing man. "Harper reached a point where he _had_ to fail or else be subject to this psychic storm." Paul ran his long, bony fingers through his hair. "This makes less sense than ever! If that's true, then we've got to take back what we've told Oglethorpe. His errorless man isn't possible, after all." "I don't know." Barker shook his head thoughtfully. "Evidently the production of error is a protection against the admission of this intolerable feedback impulse. But the question remains: why is it intolerable, and why does it become so after numerous other feedback impulses have been passed? "Yesterday we thought we had it all wrapped up. Now it's blown open wider than ever before!" * * * * * Oglethorpe's public relations man prepared a statement to the effect that further danger from pilot error in rocket ships and the second Wheel could be considered as completely eliminated with the new training processes that would make men incapable of technical errors. Paul knew it was as ineffectual as the average Government release, but he made no protest in his concern for Harper and the three other men. He signed the statement automatically. He was presented the following day, however, with arrangements to give it personally to the members of Morgan's Caravan from the top of one of the sound trucks. He did protest then that any flunky on the Base could read it to the crowd as well as he. But Oglethorpe insisted he do it personally. With official pompousness the big, olive-green truck rolled out from the Base. Paul rode beside the driver and Metcalf, the public relations man. He'd not told Oglethorpe about their latest development. If this psychic reaction to feedback proved an impenetrable barrier there'd be time enough to give Space Command the bad news. In the meantime a Wheel would be built, the public would be mollified, and Superman would continue on--to what unknown ends Paul didn't know.