Dartington Hall was built on a strong, companionate relationship between two complex, contradictory people. This chapter explores the paths that led Dorothy and Leonard Elmhirst to marry and start Dartington, illuminating a rich early-twentieth-century landscape of philanthropy, humanitarianism, spirituality and international exchange. It shows how affective relationships fuelled far-reaching collaborative reformism. The chapter also gives an overview of Dartington between 1925 and 1945. It dwells on the Elmhirsts’ desire to combine local roots with international horizons (what Kwame Appiah terms ‘rooted cosmopolitanism’); explores the implications of this progressive experiment’s setting in the conservative county of Devon; traces the project’s trajectory from a small, independent-minded venture in the 1920s to one that, by the late 1930s, aimed to contribute to state-led social reform; and situates Dartington amid myriad other unity-seeking reform projects of the interwar period, from the New Deal to Mass Observation.