[1] Her call to service in India fell from a need to have a female physician provide quality medical care to high-caste women, that were religiously secluded to zenana.
Supported by the Woman's Foreign Missionary Society[2] of the Methodist Episcopal Church, Swain left the United States in 1869, for Bareilly, India, where she spent the next twenty-seven years of her life treating women and children from illnesses, while simultaneously working to evangelize natives.
[1][3] By the end of her first year in Bareilly, Swain had acquired seventeen medical students, clinically trained under her supervision, and had treated at minimum, 1,300 patients.
Beginning March 1, 1870, these women were given clinical experience by working with the orphaned sick and "Christian village", and were taught basic lessons in "anatomy, physiology, and materia medica," by Swain herself.
Swain had spent two to three hours a day with her students, preparing them for the "examination of fourth-grade doctors," supervised under two civil surgeons and an American physician.
[1][4] Accommodating the constant influx of patients, outpatient visits, and the rapidly increasing work eventually took a toll on Swain's physical and mental health, causing her to return to America in March 1876.
[4] Although there had been indigenous resistance to Western medicine and religion in India, the mission had successfully procured an estate from the Nawab of Rampur, on which to expand medical facilities.
Such was not an uncommon thread of families of princely states, since many of them in this area were in favor of "mission-sponsored initiatives for female education or medical work."