Uncle Tom's Cabin has been denigrated, though now more often respectfully admired, as the epitome of politically effective American sentimentality, for its masterful marshaling of sympathy, identification, and affective bonding. Yet one of the novel's most powerful – but rarely analyzed – elements are a series of unsentimental dialogues about the economic, historical, and moral aspects of American slavery. Stowe sets up each scene with a specific incident (Prue's death; Dodo's beating) then makes it the occasion for the immensely likable New Orleans slaveowner Augustine St Clare to debate the issues and implications with a member of his family: his harsher brother, Alfred, or his Yankee cousin, Ophelia. The discussions are private, domestic; the calm discussants trust each other. But these aggressively American scenes are actually a terrifically skilled, much-improved rip-off of a structure and technique developed in the 1820s by the English evangelical fiction writer Charlotte Ellizabeth Tonna to depict and debate British slavery in the West Indies, a place she had never visited. Stowe wrote an introduction to the American edition of Tonna's works in the 1840s, and knew them well. In Tonna, a deeply Christian English aristocrat visits his comfortably slaveowning brother in the Caribbean, and slavery-related incidents are used to trigger lengthy fact-based brotherly debates. Frankly, Tonna's novel is very, very dull: characters aren't individualized, the plot barely exists, and the seemingly endless dialogues are earnest, religious, humorless, a substantive essay given the merest sheen of fiction. Stowe's refashioning here crosses the Atlantic twice: first to England, to appropriate a fellow female evangelical writer's fictional structure for getting distanced, rational debate into a largely sentimental novel about slavery, then to the West Indies for an analogous – but quite different – slave setting and system. My paper analyzes this triangular circulation in detail to highlight how Stowe relied on British and West Indian sources to fashion her witty, ironic, politically satiric scenes of analytical dialogue.