China’s treatment of its religious minorities, particularly the Uighurs in far-western Xinjiang province, was thrust into the limelight after a Uighur woman detailed the abuse she said she suffered in an internment camp. A Wall Street Journal investigation reveals what goes on inside China’s growing network of internment camps, where hundreds of thousands of ethnic Uighurs are believed to have been detained.

It also appears that the Chinese state is putting party members in Uighur families: The two women in the photograph were smiling, but Halmurat Idris knew something was terribly wrong.

One was his 39-year-old sister; standing at her side was an elderly woman Idris did not know. Their grins were tight-lipped, mirthless. Her sister had posted the picture on a social media account along with a caption punctuated by a smiley-face.

“Look, I have a Han Chinese mother now!” his sister wrote.

Idris knew instantly: The old woman was a spy, sent by the Chinese government to infiltrate his family.

A Uighur woman and mother of three told a Congressional committee this week that she was tortured and suffered the loss of a child in a mass internment camp.