Two years ago this week, in the Laotian capital of Vientiane, a retired UNICEF official named Shui Meng Ng and her husband drove home for dinner. As they caravaned through the crowded city center—she in the couple's beige hatchback, he in his battered Jeep—Ng lost sight of the Jeep in her rearview mirror. She has not seen or heard from her husband since.

Ng's husband, Sombath Somphone, is well known in Laos for his decades of work on behalf of farmers and sustainable farming practices. A small man with close-cropped white hair and a broad, even-toothed smile, he has a gentle poise that belies a strategic mind. At times, his patient reform efforts have even enjoyed support from the notoriously secretive