This is the first comprehensive study of the life and work of Andrew Fernando Holmes, famous for his work on congenital heart disease. Physician, surgeon, natural historian, educator, Protestant evangelical. Andrew Fernando Holmes's name is synonymous with the McGill medical faculty and with the discovery of a congenital heart malformation known as the "Holmes heart." Born in captivity at Cadiz, Spain, Holmes immigrated to Lower Canada in the first decade of the nineteenth century. He arrived in a province that was experiencing profound social, economic, and cultural change as the result of a long process of integration into the British Atlantic world. A transatlantic perspective, therefore, undergirds this biography, from an exploration of how Holmes's family members were participants in an Atlantic world of trade and consumption, to explaining how his educational experiences at Edinburgh and Paris informed his approach to the practice of medicine, medical education, and medical politics.