"Cyrus" is the work of directors Mark and Jay Duplass, who are famous for their unusual method (a scriptless process of near-total improvisation), and their unusual tone, uncomfortable comedy arising from socially excruciating situations ("The Puffy Chair," "Baghead").
By encouraging actors to take the story in unpredictable directions, they create an air of prickly intensity, edgy possibility.
But in "Cyrus" their loose reins have created confusion, at least in me. I was dogged by the feeling their title character isn't just edgy, he's in need of treatment.
There is the troubling sense that he's mentally ill, or that he has some undiagnosed developmental disorder. (The same problem that surrounded Ben Stiller's character in "Greenberg.")
The Duplasses (or Hill himself) try to play this for laughs, concocting a scene in which Reilly's character wakes up in the middle of the night and encounters a half naked Cyrus in the moonlit kitchen, holding a knife.
Invoking this cheap thriller element - like a reverse "Stepfather" - is meant to deflate our nervousness at Cyrus' behavior, and perhaps underline the difference between the far-out "Cyrus" and standard Hollywood fare.
But I never felt that it displaced the elephant in the room (apologies to Hill). Why does his behavior fail to register with his mother? She rarely mentions her son's lacks of friends, work, social contacts, and certainly has not come to terms with it.
This suggests that the Duplass method has shortcomings - a firm hand from a scripter or director might have forced Tomei's character to be more involved in what's going on around her. As it is, she seems to be the odd woman out in the game of improvisation, which Reilly and Hill (both Apatow veterans) have played before.
The winner, really, is Reilly, who's tender and funny and winning here. Hill has gotten all the attention, because his character screams for attention, but it's Reilly who gives the movie emotional substance.