This article focuses on Robert Hart during the Boxer Rebellion. My reconstruction of his activities is based on a recently discovered file in the archives of the Chinese Maritime Customs Service held at the Second Historical Archives in Nanjing. While it has long been known that Hart corresponded with Qing officials during the Siege itself and while a few letters have been published, the file contains more than one hundred exchanges between Hart and Qing officials written after the end of the Siege of the Legations. I have further relied on a box of documents dealing with the Boxer Rebellion in the Hart Manuscript Collection at the Queen's University of Belfast, including Hart's notes on his meetings with Qing officials. These materials provide insight into the way Hart was able to persuade the Qing and foreign countries to begin negotiations and illustrate the critical role he played in fashioning the Boxer Protocol signed on 7 September 1901.