During an era of separate spheres for men and women, Margaret Macdonald used her nurse's training to gain access to the military and a life of work, travel, and adventure. In 1906, she was one of the first two nurses to receive a permanent appointment to the Canadian Army Medical Corps. She became matron-in-chief of Canada's overseas nursing service during World War I with the rank of major - the first such appointment for a woman in the British Empire. Macdonald also served as a nurse in the military during the Spanish-American and Boer Wars and in Panama during the construction of the canal. Margaret Macdonald traces the life and work of this extraordinary woman from rural Nova Scotia whose sense of duty and ambition found an outlet in the imperialism of Great Britain and the US. Susan Mann weaves the threads of character, ideology, and opportunity into a vivid portrait of Macdonald and her impact on the professionalization of military nursing.