This is the first history of the Plymouth Brethren, a conservative, nonconformist evangelical Christian movement whose history can be traced to Dublin, Ireland in the late 1820s. The teachings of John Nelson Darby, an influential figure among the early Plymouth Brethren, have had a huge impact on modern evangelicalism. However, the credit for Darby's work went to some of the first generation of his students, and as evangelicalism has grown it has completely ignored its origins in Darby and the Brethren.

In this book, Massimo Introvigne restores credit to John Nelson Darby and his movement, and places them in a contemporary sociological framework based on Introvigne's participant observation in Brethren communities. The modern-day Plymouth Brethren emphasize sola scriptura, the belief that the Bible is the supreme authority for church doctrine and practice. Brethren see themselves as a network of like-minded independent assemblies rather than as a church or a denomination. The movement has also refused to take any formal denominational name; the title "the Brethren" comes from the Biblical passage "one is your Master, even Christ; and all ye are brethren" (Matthew 23:8). The Plymouth Brethren offers a typology of differing branches of this reclusive movement, including a case study of the "exclusive" branch known as the Plymouth Brethren Christian Church, and reveals the various ways in which Brethren ideas have permeated the modern Christian world.