This paper explores the use of mindset material in terrorism cases. Mindset material is a broad category of evidence, including social media activity and internet search histories, relied on to infer or imply that the accused is affiliated or aligned with terrorists. Although mindset material plays a central role throughout the justice process in terrorism cases, no work to date has explored and discussed its use in depth. In this paper I draw on doctrinal and empirical findings, including interviews, to examine how and why it has come to play such a central role in terror cases. While mindset material is a well-intentioned tool used to selectively enforce broadly drafted and vaguely defined terrorism offences, it is also a blunt tool, and sees great emphasis placed on the accused's inferred status as terrorist (or not). In this paper I explore and problematise the use of mindset material and the inferences drawn from it, specifically in relation to to fantasists, the merely curious, and young autistic defendants. I posit that mindset material is symptomatic of a need to revisit the substantive law and to rethink the proper role of the criminal law in preventing terrorism.