Born in 1751 to Charles Jean-Baptiste Sanson and Jeanne-Gabriel Berger Sanson.
Marie becomes a Prévôté de L'hôtel at the age of 11. After witnessing her successful standing decapitation of Marquis Georges de La Tour, the future Duke of Orleans Louis Philippe II takes her to Versailles to act as Prévôté de L'hôtel there.
At the age of 19, Marie engages in a lesbian relationship with the Dauphin of France Marie-Antoinette, after being made her guard by Louis Philippe. After Madame du Barry shares her concerns of Marie's influence on Antoinette with Charles-Henri, he challenges Marie to a duel. Charles-Henri promises to grant her freedom if she wins and to marry her off to the man Charles and his father have approved if she loses.
Marie puts all her strength in the duel, and attempts unsuccessfully to kill Charles-Henri. However, Marie is shot in the shoulder with a gun her brother snuck into the duel. Incapacitated and with Charles-Henri's sword at her heart, Marie agrees to marry, with the condition that she could wait until her hair had grown out before the ceremony was held.
Just prior the wedding, Marie returns to Versailles, disguised as a proper lady, and attempts to persuade Antoinette to continue her vow not to speak with Madame du Barry, as well as the relationship the two had. However, Antoinette chooses to embrace “adulthood” and finally speaks to the king’s mistress.
The wedding is held, but Marie’s betrothed, a distant Sanson named Gaspard, does not show up. Marie begs Charles-Henri to allow to her to instead marry the nephew of Nicolas Sanson, Jean-Louis, a man she claims to love. Both Andre and Nicolas Sanson persuade Charles-Henri further, and he agrees to sign the marriage certificate. A complex plot is revealed once the marriage is official. Jean-Louis Sanson was easily swayed with gifts of food, and Marie convinced him to reinstate her position as Prévôté de L'hôtel if they married. Through the help of one of Marie’s admirers, Chevalier d’Eon, Gaspard was held captive for the duration of the wedding so Marie’s plan could work. Now as a married woman, Marie tells Charles-Henri she is no longer subordinate to her brother’s decisions as Sanson family patriarch, and returns to her position as Prévôté de L'hôtel.