I liked the overall story and idea, but something was missing.... I needed to get to know the characters more, even though I realize that could potentially ruin the ending, but the reveal shouldn't be everything, and it is here. I also didn't like Anne Baxter in this film.
Twisty-twist! Sweet Wellesian cinematography and a great musical score. Pretty good cast too. Made the same year as the similarly paranoiac and inebriated THE WHOLE TRUTH, it tries with some success to emulate TO CATCH A THIEF and LES DIABOLIQUES in ways that Hammer, Chabrol and Carroll Baker gialli did.