This study combines network science and ethnography to explore how al-Muhajiroun, a banned Islamist network, continued its high-risk activism despite being targeted for disruption by British authorities. We analyze news reports, interviews, and field notes using social network analysis and qualitative content analysis to test hypotheses pertaining to network structure and performance. Our analysis suggests that the activist network’s structural properties had important implications for its performance during three separate time periods. What began as a centralized, scale-free-like, small-world network centered on a charismatic leader evolved into a more decentralized "small-world-like" network featuring clusters of local activists connected through multiple bridges. This structure allowed the activist network to engage in contentious politics even as its environment became increasingly hostile. We conclude by discussing the implications of al-Muhajiroun’s small-world solution for scholars and policy makers.