Despite its unusual setting in a mental institution, John Carney's pre-Once feature is a considerably more conventional film than his quasi-musical hit, although On the Edge carefully skirts post-One Flew Over the Cuckoo's Nest cliches, with this particular institution altogether more benevolent. Even so, the film often feels too indebted to other movies to fully spread its wings.
On the Edge's most obvious forebears are Danny Boyle's Trainspotting, with its hyperactive opening and cocksure lead character (who is then confronted with challenges that force him to grow up), and Neil Jordan's darkly humorous The Butcher Boy, which provides a shade of black reflection on the complex and sometimes violent undercurrents that lurk in Irish family life (and a nice line in raw humour).
The camerawork sometimes obscures the actors, too, which is a pity since they're generally very strong. Stephen Rea, who has played so many unpredictable parts, here gets the chance to play it straight and buttoned-down, allowing the younger actors, particularly Cillian Murphy, to make most of the running. It's not entirely clear why two young, and fairly obscure, American actors were used in the film, but Jonathan Jackson is charming (even with a sometimes oddball Northern Irish accent). Anna Manahan, better known as a stage actress, has a nice bit as one of the older inmates; by contrast Gerard McSorley, usually such a powerful presence, has an inexplicably small and wordless part.
The film sometimes stumbles in negotiating the transitions from funny to serious, though as the story progresses two of the most powerful sequences creep up almost unannounced, emerging at unexpected moments; it's notable that these scenes are visually far calmer, allowing the script and the actors to do their work. It's not that hard to guess the direction the plot will take - the film telegraphs one development particularly obviously - but the conclusion introduces a convincing element of maturity to the lead character, with Cillian Murphy playing the scene with a tenderness that his character has just learned.
Carney's background is as a musician, and as well as supplying some of the music he has assembled a tremendous soundtrack (for a small film, the rights costs must have been a major budgetary consideration). Occasionally, the musical backdrop seems overly insistent, rather than stitched into the fabric of the film, but when the sound and images work together, as in a wonderful sequence set to 'Singin' in the Rain', the film lifts off.