Stranded on a corn chopper engulfed in flames and wrapped in the deafening hum of 140,000 volts, J.P. Koop leaped into a crackling halo of current. Crashing into a smoking row of freshly cut stalks, Koop’s body went to jelly on impact, electricity surging through his limbs. On hands and knees, he made the crawl of his life.