This article provides a contextual analysis of the assassination attempt on the Timurid ruler Shāhrukh's life on 21 February 1427 in Herat. According to the contemporary Timurid chroniclers, Aḥmad-i Lur, a Ḥurūfī by profession, tried to kill Shāhrukh. Having survived the attack with light injuries, Shāhrukh reacted harshly and executed many of those who were accused of conspiring against him. During the interrogations, many other intellectuals who professed as a method of inquiry the ‘ilm-i ḥurūf (the science of letters) were also accused of participating in the conspiracy. In this article, I treat the assassination attempt as a moment of crisis in Timurid politics, study it in relation to the transformation of the intellectual landscape towards the mid-fifteenth century, and provide an in-depth textual and contextual analysis of the historiographical sources as well as the writings of those intellectuals who left a first-hand testimony of the subsequent interrogations. After a close scrutiny of the available evidence, I demonstrate that the interrogations of those intellectuals who practiced the science of letters predated the assassination attempt, and I argue that the assassination attempt was just an episode, albeit an important one, in Shāhrukh's attempts to control and regulate the emerging public sphere in Iran and Central Asia.