"The Dangerous Lives of Altar Boys" gets its title from the pranks pulled by its main characters, a pair of trouble-making Catholic school kids engaged in a never-ending battle of wills with the hard-hearted nun in their home room.

Dubbed "Nunzilla" by the boys, and played by Jodie Foster in battle-ax mode, she's a concerned but misguided tyrant in the classroom, barking about the evils of William Blake poetry and deliberately embarrassing young Tim Sullivan (Kieran Culkin). In front of his peers she rubs in the fact that he's been held back a year and suggests her class pray for his family's domestic problems.

With her painfully pinched face and her peg leg, she's also the inspiration for the motorcycle-riding, vampire-like antagonist in a comic book the boys habitually sketch out in spiral notebooks. Ringleader Tim and his sometimes reluctant adherent Francis (Emile Hirsch) are superheroes in this cartoon fantasy, which comes to life in vivid animated passages of the movie (created by Todd McFarlane of "Spawn" fame) that revel in the boys' collective imagination.

In this world they're muscle-bound mutants doing battle with a ferocious version of Sister Assumpta. But in the real world, troubled and angry Tim is leading their mischief down a perilous path, while at the same time Francis is being pulled in another direction by a pretty but tormented classmate (Jena Malone).

Adapted by screenwriter Jeff Stockwell from a posthumously published 1994 novel by Chris Fuhrman, the film is given palpable atmosphere of somber nostalgia and psychological tension by director Peter Care, whose background includes documentaries, music videos and REM's concert film "Road Movie."

Care culls deeply rendered, distinctly three-dimensional performances from his entire cast that make "Altar Boys" very engaging even though the story is never quite compelling enough to draw you in on its own. Culkin ("Cider House Rules") finds an amazing balance between knavishness, menace and sympathetic melancholy. Newcomer Hirsch becomes the audience's surrogate, drawing us into his dilemma about becoming his own man and abandoning Culkin, who eventually makes it clear it's the girl or their friendship.

Jena Malone ("Life as a House," "Donnie Darko") is quite simply one of the most innately talented teenage actresses working in film right now, and she brings a sweet sadness and uncomfortable, passive-aggressive sexuality to her role as the girl who longs to find stability with vacillating Francis.

Vincent D'Onofrio, my favorite cinematic chameleon (he was a serial killer in "The Cell," Abbie Hoffman in "Steal This Movie" and the farmer who becomes a bug in "Men In Black") has a perfectly understated supporting role as the easy-going but tough priest who runs the Catholic school. And Foster is terrifically uptight as the haggard (but too young to be a hag) Sister Assumpta.

But "Altar Boys" begins to unravel as Tim and Francis escalate their pranks, inspired by their comic books fantasies. A large part of the plot concerns Tim's wild plan to steal a cougar from a local zoo and let it loose in Sister Assumpta's office. When the plan goes awry with tragic results, the picture focuses only on regret and skips right over anything resembling consequences, practically castrating the movie's veracity in its final act.