Paris, a misty night a few days before Christmas: a young woman is saved from the waters of the Seine. She is naked, doesn't remember her name or how she ended up in the river, but is still alive. The mysterious woman is taken to the hospital - and then disappears in thin air.

DNA testing reveals her to be celebrated concert pianist Milena Bergman - but that cannot be: Milena died in a plane crash more than a year before. As police captain Roxane begins to investigate, her fate becomes intertwined with that of writer Raphaël Batailley, Milena's former boyfriend, and the two are plunged deep into an impossible enigma: is it possible to be alive and dead at the same time?