A literary true-crime investigation that tries to solve a 77-year-old cold case and ends up rehabilitating the reputation of its life model victim has won France’s most prestigious literary prize.

The author Philippe Jaenada was announced on Tuesday afternoon as the winner of the Prix Goncourt, for his book L’Inconnue du quai de Javel (The Unknown Woman of the Quai de Javel), a recreation of the murder of a 29-year-old Breton woman named Louise Cansot.

Known as “the woman with a hundred portraits” because she was so sought-after as a model for artists in Montparnasse, Cansot was found dead on 7 September 1949, but police never managed to establish the identity of her murderer.

Philippe Jaenada.…