Excellent sound, perhaps the best out of all Robbe-Grillet films with three musical motifs that dominate the film: Il Trovatore, Erika, and Carolina, with Michel Fano manipulating the sound to wonderfully weird and often sinister-sounding results. I think some of his compositions for Successive Slidings... are reused here as well.
The cast is great, and standing out as both super-creepy and funny is the late great Serge Marquand as the shady butler. And in another smaller role(s), Jacques Seiler.
Effective drinking game is to take a shot every time a character gets drugged and / or abducted in this film.