A third of the way down the blue walk he ran into the invisible electric shock wall, and staggered backward. The lunch packet that he carried fell from his hand, and he was obviously too stunned to remember to pick it up as he started back. He had retreated only a short way before he paused and stood considering his situation. After a minute he returned and examined the buildings at each side of the electrified area. He must have found that the conduction outlets did not extend to the ground, for soon he began crawling forward on his hands and knees. "A point for the alien," I heard Srtes murmur. I detected a hint of admiration in his voice. The alien kept his caution, for when the ground caved beneath his hand, at the end of the third street, he did not fall into the trap. He simply rolled back and lay quietly for a moment. Another decision. He was equal to it. Rising to his feet, he took a short run and leaped for the balcony on the nearest building. From there it was an easy matter to reach the roof. Observing carefully below before each venture, he leaped from roof to roof until he reached the end of the street. We lost him for a short time then. He had gone down into the last house. A few minutes later a guard in front of the door stumbled abruptly backward and disappeared inside. Another moment passed and the guard reappeared. He walked briskly up two streets before we became aware of what had happened. The alien had changed to the guard's clothes! That would not take him far, of course. At the beginning of the third street he was stopped by two sentries. When they demanded a password, he whipped his sword out from beneath his cloak and ran the nearest through. The second shouted for help and drew his own sword. He offered only a moment of resistance. We saw then the alien's reason for grinding down the long sword. He handled it almost like a whip, and the sentry was unable to parry his swift thrusts. As I noted the councilors' exchange of wondering glances I understood that a new weapons concept had been born. When the second sentry fell, the alien sprinted into the house, and reappeared a minute later on the roof. Soon he was a block away from the scene of the fight. The sentries at the second intersection had run back in answer to the shout for help, and the alien was able to cross the street unmolested. Once again he took to the roof, and when he came down again he had reached the Building Administrates. He was directly below us! We followed him on the screen as he ran down the stairs to the basement. A sound from the front of the building attracted our attention and we switched back. Two sentinels had not been caught off guard. They had spotted him entering Administrates and were following closely. We switched back to the fugitive, and just in time. He had dragged himself almost all the way under the bottom ramp of the stairs. Soon he had disappeared entirely. Now the sentinals were looking about in a confused way.