Inspired by her mother’s issues of the Missionary Record, Mary began to teach voluntarily at the new Dundee mission. When David Livingstone died in 1873, resulting in a nationwide call for more missionaries, Mary decided to follow in his footsteps. She set sail in the SS Ethiopia on 5 August 1876, arriving in West Africa just over a month later, aged 28. Mary was first assigned to Calabar in southern Nigeria where her duties included teaching children and working in the dispensary.