He did not rejoice. He went on without elation, but it became a part of his painstaking search for vengeance that he knew he could set off explosives within a hundred and twenty-five yards of himself. There was something about the device he'd constructed which made explosives detonate, up to a distance of a little over one hundred yards. He felt no curiosity about it, though it was simple enough. The heterodyning of extremely saw-toothed waves produced peaks of energy until the saw-teeth began to smooth out. There were infinitesimal spots in which, for infinitesimal lengths of time, energy conditions comparable to sparks existed. This had not been worked out in advance, but the reason was clear. He came to the place where the main highway to Boulder Lake branched off from the road he was following. He turned into it, walking doggedly. Three miles toward the lake, an engine sounded from behind him. He got off the highway and turned the switch. A half-ton truck came trundling openly along the road. It came closer and closer. Small-arm ammunition exploded. The engine stopped and the light truck toppled over onto its side. Lockley did not approach it. Its driver might not be dead, and he would not find it possible to leave any man alive who was associated with Jill's captors. He passed the truck and went on up the highway. Seven miles up the road a truck came down from Boulder Lake. Lockley placed himself discreetly out of sight. He turned on his instrument. A gun flew to pieces with a thunderous detonation. The truck crashed. It was interesting to Lockley that automobile engines invariably went dead at about the time that explosives went off. The fact was, of course, that ionized air is more or less conductive. In an ion cloud the spark plugs shorted and did not fire in the cylinders. There were two other vehicles which essayed to pass Lockley as he went on up the long way to the lake. Both came from the interior of the Park. He left them wrecked beside the highway. Between times, he walked with a dogged grimness toward the place where Vale had been the first to report a thing come down from the sky. That had been how many days ago? Three? Four? Then Lockley had been a quiet and well-conducted citizen inclined to pessimism about future events, but duly considerate of the rights of others. Now he'd changed. He felt only one emotion, which was hatred such as he'd never imagined before. He had only one motive, which was to take total and annihilating vengeance for what had been done to Jill.