This study investigates the origins, development, and influence of a controversial retreat movement which emerged as a self-consciously countercultural response to the socio-religious revival in early twentieth-century Québec. The movement's founder and namesake, Onésime Lacouture, S.J., developed a redaction of the Ignatian Exercises that was heavily informed by his mystical experiences and ascetic theology. The retreat was wildly attractive to some, while others saw it as overly severe, possibly heretical. The retreat endured Lacouture's personal suppression, and migrated southward to the United States, nesting among sympathetic clergy constellated around Pittsburgh. Its most prolific advocate and apologist was a diocesan priest named John Hugo, who traded blows with antagonistic critics and was himself “exiled” to a series of suburban Pennsylvanian parishes. Hugo would proselytize the retreat tirelessly, and found an enthusiastic vessel in Dorothy Day—cofounder of the Catholic Worker movement, candidate for sainthood, and an icon of contemporary radical Catholic activism. From a socially withdrawn contemplative movement—deeply opposed to mainstream Canadien assimilation into Anglo Canadian culture and the then-ascendant “social Catholicism”—the Lacouture retreat would morph into spiritual fodder for arguably the most radically socially engaged iteration of Roman Catholicism in North America. This book discusses the evolution of “Lacouturisme” and its impact on Catholic Worker theology within the contexts of the Christian ascetic tradition, Catholic engagements with “Modernism,” and spiritual transnationalism.