The book recounts CTI's initial development by a creative team of mental health and social service providers working in large homeless shelters in New York City during the early years of the city's contemporary homelessness crisis, describes the main components of the model, emphasizing how it differs from standard forms of case management, summarizes research evidence supporting the effectiveness of CTI, describes how the model has been adapted for use with different high-need populations in a variety of settings in the US an elsewhere, and considers strategies and challenges related to broader implementation of CTI including workforce training, funding, fidelity assurance, and program drift. It concludes with a consideration of the implications of CTI for the design of new "time-sensitive" intervention models in social work and allied fields.