Chemin took part in the Marquis de Lafayette's Expeditionary Corps during the American Revolutionary War. Back in France, while working at a Les Invalides hospital during the French Revolution, Chemin became a sympathizer of the Assassins and was subsequently recruited into the Brotherhood.
Later, discovering that the doctor was under Templar surveillance, the Assassins decided to establish a secure way of communicating with their new agent. Thanks to Chemin, the Assassins then learned that Payen, the man overseeing the medical procedures at Les Invalides, was in fact a high-ranking Templar. After Payen and his guards were eliminated by the Brotherhood, Chemin was captured by the Templars and taken to the Temple, where he was forced to prepare poisons for their hired killers until an Assassin rescue mission freed him.