The story of the movie is simply constructed, as it is obvious from early on, that the husband will have to do something about the confusing behaviour of his wife. When he finally has her committed in the extremely realistic but very uncomfortable scene with his mother and the family doctor, I was really wondering how the film might turn. I didn't like the way the scene at the beach was edited, but how the father totally mismanages his fatherly duties was quite a revelation.
Even though Rowlands acting was jaw-dropping I was also quite amazed by Falk's work. There is a certain subtlety in his calm behaviour that made me think that he was having substantial mood swings inside him. The story also transports that, so he works incredibly well.
I would like to look at the commitment scene again - there is a lot of movement in the scene although most of the time nobody is really moving around except Rowlands and Falk trying to contain her (and his mother).