Roger has a number of social problems that appear to long pre-date hospitalization, and although he can relate to wood (he soon fixes a swollen door) and Mahler, (whom he quickly recognizes is ill) he can't relate to people, and thinks life would be better without them.
In spite of this, Roger - who's turning 41 - tries to have sex with his brother's assistant Florence (Greta Gerwig), who's much younger, very vulnerable, and just recovering from a previous relationship. And she's nevertheless almost inexplicably attracted to Roger, but there seems to be an oppositional ideology working here: an unambitious guy in LA? like, er, wow!
Roger hasn't forgotten his former girlfriend Beth (Jennifer Jason Leigh) of 15 years previously, and whom he left for the lure of other girls, although it's clear later that the relationship mattered far more to Roger, as Beth doesn't really remember finer details of it: he's evidently barking up the wrong tree.
It's obvious that Roger will have to start thinking about others more if he wants to keep any friends, although he of course blames things on everyone else: what else would you expect from someone whose principal pleasure seems to be writing letters of complaint to any business concern he has any dealings with? He doesn't drive anymore and uses Florence and his 'best' friend Ivan (Rhys Ifans) - who's now got a computer business but was once in a band with Roger that Roger caused to fold - as chauffeurs.
His rudeness is almost unbelievable - when Ivan gets the waiters to give him a surprise serenade by singing 'Happy Birthday', Roger tells Ivan: 'Sit on my dick, asshole!', and later that evening - when Florence (who thinks the outburst is funny because meaningless) gives him a present and tells him he can stay over, he storms out after she's tells him a story about her past that he doesn't like. (And this is not the first time that there's been a suggestion of inappropriate jealousy.)
Toward the end, Ivan is almost ready to give up on Roger, and maybe it's the final straw when Roger asks him who Vic is. Vic is Victor, who's Ivan's son, and Roger immediately apologizes for not recognizing 'the diminutive form', but Ivan just turns his back and walks away.
Florence seems to read Roger's mind like an expert: even though, after they've finally had sex and she asks him if he thinks he can ever get to love her, and he says he doesn't know, just as she goes into the theater for an abortion (which is her former boyfriend's doing), she tells Roger that she thinks he likes her more than he knows.
Certainly, after a lot of alcohol, a line of coke and a little dope (and of course he Bogardes the joint), he confesses via cell phone message that he likes Florence a lot: OK, it's not direct, but hey! And he even has second thoughts about flying off to Australia with two 20-year-old girls at the last moment so he can go and meet Florence from hospital.
So, he's finally learned to grow up and move into a real relationship? Well, the screen goes blank and the credits roll before Florence hears the full message on her cell phone, so maybe it's a little inconclusive.
What is certain, though, is that this is an excellent and largely neglected movie from Noah Baumbach.