There are movies that defy categorization and characterization--films that break enough rules or traverse enough genres to become something that can't be easily summed up. Birth is one of those movies, but it's also something far simpler--a love story--and it's no easy task to figure out how those seemingly disparate parts make up its whole.

Nicole Kidman plays Anna, an aristocratic New Yorker who's engaged to Joseph (Danny Huston). 10 years ago, Anna's husband, Sean, died--and a decade later, Anna's beginning to move on. But then a brooding 10-year-old boy (Cameron Bright) walks into Anna's home, insists that he's Sean, and that he doesn't want Anna to remarry.

At first, Anna shrugs it off as a joke--but as the boy shares disconcerting details about Sean and Anna's life together, issues of loss, love, belief, and sex become unavoidable.

While Birth uses its possibly metaphysical plot to bait viewers, it hooks them with the heaviest of emotions. It refuses to shirk from the dark depths of its characters, and it's spellbinding to watch the boy's devotion and love for Anna only grow stronger, Anna's slow transformation as she begins to consider the impossible, Anna's mother's (Lauren Bacall) cynicism, and Joseph's angry jealousy. Director Jonathan Glazer (Sexy Beast) handles it all with a poised steadiness--gorgeous, lingering shots and stark yet warm compositions make the film feel simultaneously intense and subdued.

The strongest thing about Birth is its jarring impact--a seemingly ridiculous premise carried out by a skilled and confident cast and crew. But the filmmakers know they're working with a finite fascination, and for many, the success of Birth will rely upon its answer to the question it poses. I won't spoil it, but Birth's third act isn't as satisfying as it could be--mainly because of the inability for any story like this to wrap itself up with a neat, tidy ending. Those looking for an answer to all of Birth's plot points will likely be disappointed, but for those willing to invest in the themes and emotions that are clearly designed to take precedence, it's an extraordinary film--insightful, moving, and unsettling.