Not only because of Arletty, the famous.
Not only because of Jacqueline Audry, almost forgotten these days.
But also because of Yves Deniaud, who passed away too early, and seemingly overlooked. Somehow he managed to keep the plot running, the other three in sync. To me he has the traits of a comedian in this movie, an early Coluche.
I found this movie a more pleasant one than the famous stage interpretation by Harold Pinter, probably due to the actual hotel scenes in the beginning. "Hotel California" springs into mind: you can check in anytime, but you can never check out.