Collecting tribal artefacts in the late 19th century, Harvard University's Peabody Museum sought to preserve a span of American history that 18th-century frontiersmen had tried to obliterate. By the end of the 20th century, the tribes wanted their things back. Thousands of ceremonial objects were returned before curators realised that earlier conservators had doused them with arsenic to repel insects. Saving the artefacts had rendered them deadly.