BLUE STEEL: Saoirse Ronan's brilliant turn as the titular teen in Hanna is equal parts fish-out-of-water youngster and cold-blooded killer.

[ CITY PAPER GRADE: A- ]

If Hanna were called Harold, no one would give a shit. If rogue asset Erik (Eric Bana) raised a scrappy son, not a fragile, lethal daughter, as his spy/assassin scion, it'd be viewed as a negligibly subversive action romp, a sweet Harry Chapin-meets-Jason Bourne paean to father-son relations. But Hanna is no boy. She's a towheaded 16-year-old menace — played by the incredible young actress Saoirse Ronan — and she'll cut your throat before you even begin to tell her how pretty her hair is. Joe Wright's fourth feature serves up Bildungsroman tropes in a most peculiar fashion, posing the question: How fast does a little girl come of age when she's being tracked across several continents by professional hit men?

Early on, Erik, framed by the CIA — vicious southern belle Marissa Viegler (a scenery-gnawing Cate Blanchett) is the architect, in stylish heels — tells Hanna that she alone holds the power to decide whether to abandon their secluded Arctic training grounds and venture out into the booby-trapped world. Stricken with adolescent ennui, Hanna throws the switch, setting off a clamorous series of events as she slips through the fingers of wranglers (see Tom Hollander's weird, fervid turn as a tennis whites-wearing gun-for-hire) who can't understand how this unassuming kid is such a tireless Run Lola Run-esque machine.

Like any good spy, Hanna speaks multiple languages, is handy with a blade and can hew to a dangerous situation in milliseconds. But unlike any well-adjusted teen, she's never seen television, is flummoxed by fluorescent lighting and responds to the innocent advances of a boy by throwing him into a neck-snapping headlock. Such fish-out-of-water play works so brilliantly here thanks to the dual efforts of Ronan and Wright, who worked together on 2007's Atonement. Though she's a seasoned killer, Hanna's spooked by the very things — friendship, family, fealty — most of us lean on in times of duress, and Ronan does amazing work coloring in the white space of this empirically directionless character. And while Wright tends to spread on his metaphors thick, his urbane eye is the enamel lacquered over the riskiest, most original major release of this young year.