In an office in a sunny, picturesque town near Bogotá, Colombia, a deceptively avuncular older man is speaking with a beautiful young woman, Maria, inquiring if she scares easily. Poised and assertive, she replies no. By the time the tense and unsparing "Maria Full of Grace" is over, her courage will be put to the test severely — over and over again. Maria (Catalina Sandino Moreno) may falter in her confidence but never backs down.

Maria has come to the office of the silver-haired Don Javier (Jaime Osorio Gómez) in the hope that he will hire her as a mule, which means swallowing up to 60 thumb-size pellets of heroin to smuggle them into New York on a flight from Bogotá in return for $5,000. The first of many strengths in Joshua Marston's fine film is that with succinctness yet thoroughness he makes entirely credible, even logical, that so lovely and intelligent a young woman should take such a drastic step. In the process the film also makes a devastating implicit critique of life for the impoverished in drug-ridden Colombia.

Maria's community is a one-industry town supported by an immense rose plantation and factory, which exports the flowers on a massive scale. The factory, where Maria strips thorns off rose stems, is light and airy, but it's a classic Third World sweatshop where strictly supervised workers are prodded to meet their quotas. Not feeling well and refused a bathroom break, Maria rebels and quits — infuriating her mother and sister, a single mother, because her paycheck is earmarked for the support of her baby nephew. To them everything else pales before unquestioned family loyalty.

Maria fares no better with her unambitious and unsympathetic boyfriend (Wilson Guerrero). Determined to pursue a better life, she is soon hitching a ride to nearby Bogotá with a young man, Franklin (Jhon Alex Toro), and he in turn is proposing to introduce her to Don Javier.

Once in New York, Maria has her self-possession put to its first major test, maneuvering past suspicious customs officers. Now her adventures are to begin in earnest, so harrowing and revealing that they won't be disclosed here, but Maria, with her daring and equal capacity for reflection, will strive to meet them head-on.

Marston shows what it means to be a mule with such step-by-step completeness that it's difficult to imagine that a documentary could be more detailed. It is a measure of Maria's desperation, her total lack of viable alternatives, that she should risk her life — all it takes to cause death is one leaky capsule — and at the same time place herself in the hands of murderously ruthless individuals.

A strong indictment of international drug trafficking and its myriad causes, "Maria Full of Grace" nonetheless is no tract but a perceptive evocation of an appealing young woman undergoing self-discovery under the most dangerous circumstances. Sandino Moreno may be in only her early 20s, but she is able to draw upon her considerable talent and training to create a portrayal that comes from deep within. She has a radiant screen presence that could give Salma Hayek a run for her money.

In his feature debut Marston reveals that crucial gift of blending acute observation with spontaneity, leavened with humor and compassion. One of the best moments in the film occurs when Maria takes notice of a New York flower shop filled with roses. Marston pauses just long enough for the implications to sink in — and not a second more.

Marston's casting sense is unfailing right down the line. Yenny Paola Vega is Blanca, Maria's best friend, pretty, headstrong, a little chunky, well-meaning but not nearly as smart or nervy as Maria. One of the film's choicest roles falls to Patricia Rae as a kindly New Yorker originally from Colombia herself, who loves her homeland but is glad she fled it, given its present state, and is grateful for the opportunities New York has provided, no matter how hard she and her husband must strive to stay afloat.

The contrast between Maria's hometown and Jackson Heights, Queens, the film's key New York locale, could hardly be more jolting visually, yet they are connected by the universal and eternal day-to-day struggle for survival on the part of those on the lower rungs the socioeconomic ladder. What's more, in its vitality and finesse, "Maria Full of Grace" is all of a piece — and both artistically and spiritually itself full of grace.

'Maria Full of Grace'

MPAA rating: R for language and drugs use

Times guidelines: Adult themes, situations; too intense for youngsters

Catalina Sandino Moreno...Maria

Yenny Paola Vega...Blanca

Patricia Rae...Carla

Wilson Guerrero...Juan, Maria's boyfriend

Jhon Alex Toro...Franklin

A Fine Line Features release of an HBO Films production. Writer-director Joshua Marston. Producer Paul Mezey. Cinematographer Jim Denault. Editors Anne McCabe, Lee Percy. Music Jacobo Lieberman, Leonardo Heiblum. Costumes Lauren Press, Sarah Beers. Production designers Monica Marulanda, Debbie De Villa. In Spanish with English subtitles. Running time: 1 hour, 41 minutes. At selected theaters.