Having followed the brilliant virologist Régnier from Montreal to Marseille many years ago, Sadie now works as a researcher in a lab, spending most of her time among microscopic creatures who teach her about life as a parasite. By day, she pushes the limits of her understanding alongside Régnier, who taught her that to study viruses, she must think infectiously, allow herself to be contaminated by dangerous ideas. By night, Sadie loses herself in bars, music, drugs, sensuality. Until she gets a call from the past that lures her back across the Atlantic. When her estranged father tells her that a bizarre virus has been found in his hospital, Sadie returns to Montreal and her family, and all the unexpected changes time has wrought, to solve this new puzzle. Soon she realizes that the person she thought she was--someone who can leave everything behind--no longer exists. What is left for her instead is sinking into the unknown to find out what happens when ideas come to life. This is a deeply inventive and singular novel about the power of metamorphosis and symbiosis. Combining the cerebral and the sensual, Sadie X explores humanity's relationship to the rest of the world, and the role of rationale--and its limits in our multilayered, regenerative existences.