A person who had usurped the identity of a famous writer of detective stories was killed in the train. Why and by whom?

Renée Saint-Cyr
Clarisse Coquet

Henri Guisol
Armand Le Noir

Pierre Renoir
Charles de Bruine

Michel Vitold
Nazarian

Raymond Bussières
Griset

Alexandre Rignault
Avril

Marguerite Pierry
Mademoiselle Malvina

Lucien Gallas
Léopold

Léonce Corne
Pincet

Guy Decomble
Jean Didier
Francis
Maurice Dorléac
Philosopher

Gabrielle Fontan
Le Noir's concierge

Richard Francœur
Commissioner

Paul Frankeur