AKA So Sweet....So Perverse - Umberto Lenzi became the Master of Italian Giallo in the 1970's and this is an early entry.
Trintigrant plays Jean a rich business man trapped in a loveless marriage with cold remote Danielle (Blanc) who turns a blind eye to his affairs until Nicole (Baker) moves into the flat upstairs,
She appears to be in a violent abusive relationship with Klaus (Frank) that she cannot escape from and one thing leads to another with Jean.
Of course this being a Giallo the whole thing is a set up and the rest of the film is working out each characters motivation with endless crosses and betrayals.
It takes its inspiration from Les Diabolique and then complicates even that and this is the films major flaw. There are just too many over-complications so after a while you begin to lose focus. There are also several inserts/flashbacks and its never explained how they fit into the main plot- and the ending makes no sense whatsover.
Baker is very good as the femme fatale and is Blanc as the much put upon wife and it looks very stylish - fortunatly Lenzi would hone his trade so this is an interesting if not that succesful go at the genre - 3/5