In 1863, at the most critical moment of the North American Civil War, the members of the diplomatic mission that President Lincoln sent to Santiago de Chile became the unexpected heroes of one of the most overwhelming tragedies in contemporary world history: death of more than two thousand women trapped and burned in the fire of the Church of La Compañía. This unprecedented catastrophe made the front pages of the New York Times and unleashed condolences from international authorities, but given the ecclesiastical jurisdiction of the time that protected priests from any civil investigation, the milestone was closed as a simple accident and the victims never obtained justice. Was it really an accident? Was there premeditation or was there negligence? The Mailbox of the Impuras reveals for the first time who the "Daughters of Mary" were, the brotherhood of bourgeoisies and aristocrats that managed to move thousands of faithful in each religious celebration but that ended up buried under the ashes of the Jesuit temple in the unjust silence of patriarchal subjugation. Their bodies were buried and burned, but not their voices, because only one thing was saved from the horrendous fire: the mailbox where the associates confessed to the Virgin their most intimate desires and sins... and also the violent abuse to which they were subjected in the supposed Name of God. Through Fátima Aguirre Vanderbilt, a Chilean-American, and the enigmatic lawyer Maximilian Bonecraft, we travel through the frenetic prelude of the thirty days before the tragedy to understand the evil behind the imminent disaster and the love that makes its way through all adversity. While in the north of the continent they fought with bullets to free slaves, in the south thousands of innocent people sought their own liberation among the flames, which they would achieve by saving not their souls, but their impure letters.