Nathalie was born in 1964 aboard the USS Maddox. Her mother Zenia, pregnant with her, was heavily wounded and was brought onboard to be treated but unfortunately died in childbirth. Her father, Borish Pash, named her before handing her to the Templar Warren Vidic to be raised by him. In exchange for saving his daughter, Pash was made to hand all his research on Project BLUEBIRD to Vidic, who was eager to learn about genetic memory.
During the following years, Nathalie was raised by Vidic while he expanded his understanding of the genetic memories to the point where he was able to create the early prototypes of what would one day become the Animus. However in 1977, Vidic made Nathalie his test subject, who through the memories of her father discovered that she was in fact a hostage of the Templars. Seeking revenge, the 13-year-old girl stole a copy of the Animus blueprints and gave it to William Miles before fleeing Vidic's lab with the Apple of Eden that Pash used as a bargaining chip to save the life of Zenia and their child back in Vietnam.
Doctor in Switzerland
By 2017, Nathalie, now an adult, had moved to Switzerland and become the director of the Clinique des Rameaux. In October, an amnesiac girl was admitted under the name "Elisa Bouvyer" by her parents. Nathalie treated the girl to the best of her ability. Some time later, the specialist doctor known as "Florent Carpentier" visited the clinic to treat Elisa. Nathalie however, saw through his disguise, identifying him as the Assassin Tomo Sakagawa who was searching for the Templar agent Maxime Gorm. Revealing her own Assassin allegiance, Chapman informed Tomo of Gorm's capture and experiment in 2000 by Thomas and Alice Adler, Elisa's parents, to which she suggested they should keep Elisa under their care. However, Tomo did not agree with essentially holding Elisa captive as it wasn't the Assassin way. Chapman informed Tomo of her plan to eliminate Gorm and destroy the Adler's research, which he agreed under some convincing. Later on, Nathalie had Tomo relive the memories of Alekseï Gavrani for her research.
In the following month, Chapman subjected Elisa to a prototype Animus she had built in an attempt to brainwash her. She also experimented on her other patients, intending to wipe their consciousness and replace them with long dead Assassins, as a form of permanent Bleeding Effect. However, her plan was discovered by Tomo, who vowed to put a stop to it. The next day, Natalie received news from her security officer Stanislas that Tomo had been killed by Gorm, and that Gorm and Elisa had escaped. Chapman returned to home, discovering that it had been broken into. Finding an Assassin inside, Nathalie feigned innocence. As the Assassin prepared to kill her, he was shot in the back by Stanislas. Nathalie then told Stanislas that she couldn't continue her research with the memories of Gavrani. She also required Maxime Gorm, and it was vital that she locate him before the Assassins do.