Presenting an analytical account of the relational dynamics linking the 2014 Umbrella Movement and the 2019 anti-extradition protests in Hong Kong, Pro-Democracy Contention in Hong Kong aims to explain not only the relationship between two spectacular protest campaigns but also why the anti-extradition protests exhibited a high degree of internal solidarity and public sympathy toward confrontational and at times violent protest actions. The analysis moves beyond the typical focus on the peaks of social mobilization to examine the contingent and dynamic evolution of the pro-democracy movement in Hong Kong. Drawing upon a range of research materials, including in-depth interviews with protesters and leading activists, surveys of protesters conducted onsite, population opinion surveys, systematic analyses of media materials, and examination of the verdicts of protest-related court cases, Francis L. F. Lee offers theoretical insights on various important issues in the study of social movements, including, among others, the possibility of movement transformation during abeyance, the relationship between protest events and elections, the role of ideological brokers in movement dynamics, and the nature of spontaneous protests. Readers interested in Chinese and Hong Kong politics or interested in social movement studies and analyses of political dynamics in hybrid regimes will find value in Lee's analysis.