Hanna (Saoirse Ronan) and her father Erik (Eric Bana) live in the icy forests of Finland, killing their own food, free of most technology (guns being the peak of progress). When she is not going through physical endurance, fight training, or hunting, her father reads to her from an encyclopedia to teach her about the world. They are training for the day when Erik and Hanna will return to civilization separately, with plans to take out an FBI agent named Marissa Wiegler (Cate Blanchett) who seems to have betrayed Erik, although the story is vague. When Hanna is ready, she flips the switch on a transponder that indicates Erik is alive, and the two go on individual cross-country, cross-continental journeys fraught with danger and the threat of death.

Make no mistake: in terms of performance, the film belongs to Ronan. With large, expressive blue eyes and an unswerving sense of purpose, she inhabits the character fully, handling each and every challenge writer/director Joe Wright places in her way with an effortless ease. Ronan's most impressive trick is blending the emotional lines between trained soldier and innocent youth, making sure to encapsulate one inside the other at all times. On her mission, Hanna meets a traveling family (Olivia Williams, Jason Flemyng, Aldo Maland) when she makes friends with Sophie (Jessica Barden), a girl the same age. The two form a unique, brief bond of friendship that both actresses play with just the right touch, letting a softer side of the character in without fully switching gears from the central story.

Without technology, Hanna's trip into the real world is one of discovery, and Wright uses that unexpected sense of wonder to create a landscape of visual and aural chaos. On her first night in a real city, Hanna finds herself confounded by the appliances in her room, which crackle, hiss, blare and beep in a unique symphony of sounds, while the more adjusted Bana is afforded a fluid, unbroken tracking shot illustrating his skill at hand-to-hand combat. Wright is aided greatly by a score from The Chemical Brothers, which fits perfectly around Wright's visuals. Some of the score is present in the film's theatrical trailer, and it feels awkward and out of place; it's nice to know that the band viewed the opportunity as a chance to record a film score than a chance to have a movie studio bankroll a new album.

There are a few nitpicks, such as the unresolved fate of a few characters, but they're minor nitpicks in the bigger picture. Although Hanna does not pack any revelatory moments, film-making is more than the story being told. Hanna utilizes simple ideas, a set of game performers, dream-like cinematography and a library of sound effects and music to create a full experience, taking the viewer on a specific artistic roller coaster. The film is punctuated by conclusive beginning and ending title screens that box in the experience; like the main character of the movie, this is a fine-tuned machine of a movie that won't stop or slow down for anything until its mission is complete.