In a 1683 sermon, Benjamin Calamy, an Anglican priest, claimed that the separation of Dissenters from the Church of England was unjustifiable. Thomas Delaune, a London Baptist schoolmaster, responded in A Plea for the Non-Conformists (1684), which compared seventeenth-century Dissenters to sixteenth-century Reformers who had escaped from the “Church of Rome.” The Restoration authorities judged the book to be a seditious libel, for which Delaune was arrested, tried, and imprisoned in Newgate, where he was soon joined by his poverty-stricken wife and two children. By 1685, the whole family had perished in Newgate. This tragic story guaranteed Delaune's status as a martyr for generations of Nonconformists. Indeed, the Plea achieved amongst Dissenters the reputation of an “unanswerable” text. Its enduring appeal transcended denominational and geographical boundaries. This paper explores the eighteenth- and nineteenth-century reception of the Plea, which Dissenters, both in England and America, repurposed for various politico-theological circumstances. Throughout the eighteenth century, Dissenters invoked the Plea against perceived cases of episcopal tyranny. By the pluralistic nineteenth century, however, this external, episcopal threat had largely been replaced with an internal one, prompting Dissenters to deploy the Plea against corruption and lethargy within their own denominations.