Marta invites Victor, whom she had met only a few days before, to dinner at her Madrid apartment while her husband is away on business. After Marta's two-year-old son finally falls asleep, the two retreat to the bedroom. As they start to undress, Marta is taken violently ill. Inexplicably, she dies.

What is Victor, a stranger in a strange apartment, to do? He removes the tape, with its compromising messages, from the answering machine, puts some breakfast food on the kitchen table for the child, and leaves.

While Marta's elderly father is disconsolate in the belief that his daughter died alone, the rest of the family is all too aware that someone was sharing her bed that night. Dean, the widower, is determined to find out who it was. All might have remained undiscovered, but Victor cannot endure living with shadows.

Marias casts a knowing eye on the secrets that bring couples together and break them apart - the admissions that conceal, the lies that reveal - and the infinite capacity for self-deception in pursuit of love.