William Tomison, in charge of the Hudson's Bay Company's Cumberland House on the Saskatchewan River, described the devastating smallpox epidemic of 1781 and 1782. He understood contagion, practised isolation and disinfection, and provided mortality statistics during a 'virgin soil' epidemic. Above all, he showed remarkable compassion. He and his men took dying Indians into their already crowded quarters, and provided them with food, shelter and 24 h care. This article describes the epidemic and its aftermath.