LYON, France—Nine days after her husband disappeared on a routine trip to China, Grace Meng frantically dialed a contact at Interpol, the global police agency, to report him as a missing person.

His name? Meng Hongwei. Job title? President of Interpol.

Ms. Meng, the wife of the senior Communist Party member, had received an ominous alert from her husband, one of the world’s top cops. His last text to her, at 12:30 p.m. on the September day he arrived in Beijing, was “wait for my call” followed by a butcher knife emoji.

The message was clear to her. He had run afoul of China’s powerful president and was heading to prison.

For a week she hoped for his release, likely accompanied by an apology for falling short of Communist Party ideals. Then, his Chinese support staff at Interpol’s Lyon headquarters stopped answering their phones. Next, a phone call from a male voice threatened her in Chinese. “Don’t talk, just listen,” he said. “We have two teams coming for you.” Her home security alarm went off several times that day.