Mr. Nhem’s gold-­plated watch glinted under the fluorescent light. He clasped his hands and smiled at me over his knuckles.

“I can help you,” Samithy translated. “I can make you famous.”

This was my opportunity to become an investor in Mr. Nhem’s museum, and thus a permanent partner. He had everything—the land, the government permits, approval for the development of fourteen identified points of interest. Mr. Nhem raised a collection of papers in a plastic book-report cover and flipped through them. He pointed to their stamped official seals. I was in a portable office in a dirt lot in northern Cambodia, and a former Khmer Rouge cadre was offering to make me a partner in the Khmer Rouge Museum.

Mr. Nhem had all the artifacts: over three hundred photos from the Khmer Rouge era and the post–Khmer Rouge fighting. He had a pair of Pol Pot’s shoes, and part of a statue that was once displayed in Anlong Veng, the town we were in. He even had the camera he’d used when he’d worked as a photographer at the S-21 prison, the infamous detention and torture center where he’d aided in documenting the fourteen thousand people who came through the facility, only seven of whom survived. He’d dubbed the relic “the Genocide Camera.”

All he needed was investors, he told me. This was my opportunity, he said. They could advertise me as “the American partner Lauren”; I could display my nation’s flag, along with a sign that said I had cooperated to support the museum. I asked how much he was looking for. An animated exchange sparked between Mr. Nhem and Samithy, the translator and tour guide who’d brought me to Anlong Veng, who’d tracked down Mr. Nhem and scored me this meeting in his mildewed office.

Samithy wrote down a figure and slid the piece of paper my way: $120,000.

Mr. Nhem had clearly mistaken me for someone other than a preschool teacher living on eight hundred dollars a month in Phnom Penh. But I decided it was better not to say this.

*

Anlong Veng is a dusty, sweaty slab of no-man’s-land in northern Cambodia. It’s one of those towns you’d pass through on a bus to somewhere better, and nothing about its battered storefronts, rubbled roads, or shabby markets squatting beneath beach umbrellas would make you think it was anything special.

The region had been the last stronghold of the Khmer Rouge, the genocidal regime under which nearly a quarter of the Cambodian population perished between 1975 and 1979. For almost thirty years after the official fall of the Khmer Rouge to Vietnamese forces, the regime remained active in the countryside, attracting devotees and...