Jean-Dominique Bauby (MATHIEU AMALRIC) is the 43-year-old editor-in-chief of Elle Magazine who's awakened from a 3-week coma following a stroke. Completely paralyzed save for the ability to blink one eye, he's shocked that those around him, including neurologist Dr. Lepage (PATRICK CHESNAIS), can't hear what turns out to be just his inner voice.
Realizing that his mental functions still seem intact, Lepage assigns physical therapist Marie Lopez (OLATZ LÓPEZ GARMENDIA) and speech therapist Henriette Durand (MARIE-JOSÉE CROZE) to begin what will certainly be a long road to an uncertain recovery. Henriette devises a process for him to communicate -- reciting letters for him to chose, with the blink of his eye, in order to form words and then sentences.
It's understandably frustrating for him, not only because it's painstakingly slow, but also because it forever changes the way he'll communicate with the mother to his three children, Céline Desmoulins (EMMANUELLE SEIGNER), and means he probably won't ever be able to visit his elderly, apartment-bound father, Papinou (MAX VON SYDOW).
Realizing he still has his memories and imagination, Jean-Do, as he's known to friends and family, retreats into flights of fancy, both about himself and his past, but also those around him, including his lover, Inès (AGATHE DE LA FONTAINE), who can't get herself to see him in this new state.
Things look up when Jean-Do realizes he still has a contract with a publisher to write a book, and thus is teamed with Claude (ANNE CONSIGNY) who then transcribes his memoir, letter by letter. While dealing with his "locked in" state that he equates to being trapped in a diving bell underwater, Jean-Do reexamines and reassesses this new life that's been thrust upon him.