On the morning of Oct. 15, Mehdi Hashemi Rafsanjani drove up the mountain road to the grim prison in northern Tehran, Iran, where he is serving a 10-year sentence for financial corruption. He was returning after a brief furlough.

Swarms of anti-riot security forces, holding batons and guns, had taken position in the leafy area outside Evin Prison, a feared institution that has been a watchword for the torment and execution of those who have displeased the Islamic Republic’s rulers.

Hashemi Rafsanjani, the son of a former president, was stunned when prison authorities told him to return home until further notice, according to family members. Authorities told him they could not guarantee his safety in the section where he was being kept, Ward 7.