After the first World War, Fraser and his wife Eileen arrived at Yilu (now Lui) in 1920. He started working among the Moru people of South Sudan. His military experience served him well in opening a hospital at Lui, which served all of Moruland--a total of 15,000 square miles.
Fraser trained young Christian converts as evangelists, teachers and medical workers, providing them with standardized medical kits and sending them out in pairs. Specific routines and procedures were established and these teams were required to send back reports to Fraser at Lui hospital at regular intervals.
Fraser also established schools and churches all over Moruland at intervals of fifteen miles along the main roads. These centers, in every part of Moruland, served as churches and schools as well as dispensaries at the same time. As dispensaries, these centers served the hospital at Lui.
An industrious and generous Christian, Fraser organized leper colonies. In addition to being a very successful surgeon, he sought to reform harmful indigenous practices and customs. All of these achievements won him a legendary status. More than any other culture in southern Sudan, Christianity deeply penetrated the Moru culture, where the people also boast a high level of education, thanks to his tireless efforts.