“Crowd Involvements and Attachments,” analyzes and classifies group affect and other forms of thinking together, such as Heraclitean flows of group thought, sensation, and experience made available through new structures of collective feeling. The chapter counters arguments about the role of the leader with the proposition that the crowd may behave as an assemblage governed by an attractor, figured by characters such as James Wait, aboard the Narcissus, or Stevie in The Secret Agent. The function of Bloom for the crowd in “Cyclops” speaks to the crowd’s management of its anxieties and their effects. The chapter explores the interpenetration of public and private spaces in Sean O’Casey’s plays to understand crowds’ precise attachments to and exercise of design over the histories and semiotics of the metropolis, testing whether and in what manner they gain the sense of a shared life and act as a performative mass body.