Three out of Five stars
Running time: 91 mins

Watchable relationship comedy with terrific performances from John C. Reilly and Jonah Hill and a handful of darkly funny moments, though the script is frustratingly slight in places and refuses to explore its central relationships in any depth.

What's it all about?
Written and directed by ex-mumblecore duo Jay and Mark Duplass (who made the excellent The Puffy Chair), Cyrus stars John C. Reilly as John, an LA film editor who still hasn't gotten over his divorce from ex-wife Jamie (Catherine Keener) after seven years. When Jamie tells John she's getting remarried, she takes him to a party to help him move on and, somewhat improbably, he hooks up with the gorgeous Molly (Marisa Tomei), who seems to really like him but won't let him see her apartment.

The reasons for Molly's secrecy soon become apparent when John meets Cyrus (Jonah Hill), her 21-year-old son, who's still very much emotionally attached to his mother and doesn't want her settling down. It quickly becomes clear that jealous, manipulative Cyrus is a bit of a sociopath and soon the pair are locked in a battle for Molly's affections.

The Good
John C. Reilly and Jonah Hill are perfectly suited to playing emotionally stunted man-children and they excel themselves here; the scenes where they square off whenever Molly is out of earshot are the funniest moments in the film. There's also strong support from Marisa Tomei and Catherine Keener, though in both cases it seems like their pre-established onscreen personas are doing all the work.

The Bad
The film's biggest problem is the script's steadfast refusal to explore the central relationships – it's impossible to believe, for example, that Molly is completely unaware of Cyrus's behaviour, so why does she turn a blind eye to it?

Similarly, John has emotional problems of his own but these are completely ignored as soon as he meets Molly and the film never bothers to address them. This would be fine if the film was more interested in broad comedy (man-child vs man-child, a la the ostensibly similar Step Brothers), but it never goes that far and, worse, the biggest confrontational moments are all in the trailer.

Worth seeing?
Cyrus is worth seeing for the blackly comic performances from John C. Reilly and Jonah Hill, but the script fails to properly explore its premise and the end result is ultimately underwhelming.