THA BAK, Laos — He was up there somewhere, at the top of the hill, the man Karl Ammann had come to see. It would soon be night. The forest was all shadows and sounds. Ammann had driven across the country to reach this remote river village, and now he was finally here, looking to the top of the hill, ready to confront the person he believed had murdered more tigers than anyone in Laos. In the distance, he could hear them: dozens of tigers roaring.