I Remain in Darkness unveils the heartrending journey through Blanche's diminishing world as Alzheimer's disease slowly erodes her essence. The initial tremor of alarm strikes in the summer of 1983 when Blanche suddenly collapses. Once whisked away to the hospital, it is revealed she has been languishing without food or drink for days. This awakening leads Ernaux to realize her mother is no longer self-sufficient, prompting her to open her home to Blanche and her sons. By the time Ernaux pens her first journal entry in December, the shadows of forgetfulness have already begun to engulf Blanche. As January 1984 dawns, Blanche's ability to write slips away, her final penned words bleakly stating, “I remain in darkness.”

February of 1984 finds Blanche, frail and resisting nourishment, succumbing to institutionalization at Pontoise Hospital. There, the ward is a somber place, occupied by other elderly souls whose bodies and minds are similarly frail. Her stay continues until mid-May, interrupted by a brief, ill-advised transfer to a private nursing home, which proves to be more troubling. Thus, she returns to the long-term care ward at Pontoise.

The following year maps out Blanche's further descent. Ernaux observes that Blanche seems to have relinquished her grip on life. She misplaces her belongings without a care to retrieve them. Yet, remnants of her old spirit linger, as Blanche expresses her yearning to be at home rather than confined to a hospital, subtly laying guilt upon Ernaux for her absence. The hospital, with its scant facilities for relief, offers little solace. Blanche's days are marked by watching television, eating, or brief excursions in the garden. By 1985, Blanche's deterioration is severe. She becomes almost entirely dependent, unable to perform basic tasks like walking or feeding herself, increasingly resembling a child or even an infant in Ernaux’s eyes.

Amidst her mother's decline, Ernaux continues navigating her own life. She embarks on trips, attends cultural events, finalizes a divorce, entangles herself in an affair, teaches, writes, and garners literary accolades. These personal milestones, however, are mere backdrops as Ernaux remains singularly focused on deciphering her emotions, particularly the profound bond with her mother.

During this turbulent period, Ernaux resolves to craft an autobiographical novel centered around her mother. This endeavor swings between therapeutic and paralyzing, as the image of her mother etched in her mind starkly contrasts with the reality of her mother's hospital imprisonment.

Blanche's life fades away in April 1986, leaving Ernaux enveloped in sorrow. Overwhelmed by grief, reading becomes impossible, and her thoughts persistently orbit around the significance of her writings about her mother. Every place she visits and every act she undertakes becomes a poignant reminder of her enduring absence.