While waiting for the brain surgery of his daughter Angela, victim of a motorcycle accident, the surgeon Timoteo (Sergio Castellitto) recalls his torrid affair with and passion for Italia (Penélope Cruz), a simple woman from slums in the periphery of the big city where he lives. The ghost of the beloved and sexual object of desire Italia chases him in his memories.
A Ukrainian woman named Irena calculatedly insinuates herself into the lives of a young, affluent Italian family. Stopping at nothing to become the couple’s trusted maid and the beloved nanny to their fragile young daughter, Irena risks everything in her quest to uncover the truth about the family. Like an intricately constructed jigsaw puzzle, The Unknown Woman reveals piece by piece the enigma of Irena’s past.