The famous scene in the swimming pool still haunts me from time to time. I've rewatched it and there is really nothing in the picture that would make you scare. It's the simple economy of Tourneur to push us into the pool with the poor lady and become witness and part of her (not so) imagined terror. Even though the woman is not the leading lady, and she doesn't come off as meek and devout as the typical victims in newer horror flicks usually seem to be, especially of the female kind.
I was very fascinated by the scene in the restaurant where the other "cat" immediately identifies the suspecting, but unbelieving girl. The short exchange is great, and the crowd's ignorant reaction was quite realistic, as the scene did much more for the viewer than anybody else. The woman already knew of her condition in a way and the others remained unknowing, therefore the scene was only for building up suspicion.
There is a notion of "saved by the bus" somewhere - defined by Wikipedia the following: " Any scene in which tension is dissipated by a mere moment of startlement, a boo!, is a 'Lewton Bus'". Well now I know.
There are some amazing shots again in this one. The first thing I liked was the darkened apartment on their first meeting, and, obviously, the swimming pool.