New Delhi, June 6 -- A shocking case in China has surfaced after 32 years. In 1992, a man named Li, then 29, killed his mother and 17-year-old girlfriend using a kitchen knife in his home in Weiyuan, Sichuan.

The man then ran away. For years, the police couldn't trace him due to poor technology and lack of leads. Last year, investigators reopened the case and found something odd.

Li's sister-in-law, surnamed Gu, also disappeared two months after the murders. She was never reported missing as she had a strained marriage with Li's elder brother. A village rumour suggested Gu and Li had an affair.

In 2013, Gu visited her family, saying she had children but didn't reveal her location. Police traced her through an old phone number and track...