investigates the troubled last years of tenth Imam ʿAlī al-Hādī and his son al-Ḥasan al-ʿAskarī. Hādī faced challenges from esoterist bābs claiming authority, most notably the renegade agent Fāris b. Ḥātim, who posed such a threat that Hādī ordered his assassination. Such challenges were compounded by a bitter succession dispute catalyzed by the unexpected death of Hādī’s designated heir, Abū Jaʿfar Muḥammad. This created confusion in the community, and doubt about the next Imam, al-Ḥasan al-ʿAskarī. Ḥasan was accused by his opponents of lacking the requisite knowledge to be an Imam, dogged by his infertility, and opposed by another brother, Jaʿfar. This dispute over Imamic succession generated a feud which was to continue after Ḥasan’s death and create a fundamental flaw between pro-Jaʿfar and anti-Jaʿfar camps that split both the family of the Imams itself, as well as their followers, and defined the development of the Twelver Occultation.