Director Gillian Armstrong has a talent for visual imagery, and she makes a powerful impression with the opening shot of "Charlotte Gray" -- a field full of bright purple flowers, blurring past the window of a train car. All by itself this image evokes an emotional reaction that primes the senses for what should be a powerful melodrama about war and love.

But the story that follows -- about a Scottish woman who becomes a World War II espionage courier in the hopes of finding a pilot boyfriend shot down over France -- is so prosaic and tainted with narrative missteps that it feels black-and-white compared to that almost magical title sequence.

The always-captivating Cate Blanchett stars in the title role, reuniting with Armstrong, who directed her breakthrough performance in the vibrant, unconventional period romantic tragedy "Oscar and Lucinda" in 1997. But lightning doesn't strike twice, and for the first time in her career Blanchett's potency seems watered down in a role that goes through the paces of being intense and passionate without actually inspiring any feelings.

Early in the film she meets an English pilot so generically handsome and one-dimensional that the moment you lay eyes on him, you know she's going to fall for someone else within a couple reels. Armstrong quickly establishes their affair with effective romantic shorthand (a meaningful stroke of her cheek, brushing her hair from her eyes during a longing stare), then dismisses the flyboy to battle.

Fervent about the war and worried sick when word comes that Mr. Wonderful has been lost over Southern France, Charlotte is ripe for recruitment when she meets a bookish spymaster who learns she speaks fluent French and nudge-nudge-wink-winks her to sign up as a spy.

The movie then skips right over exploring Charlotte's fears and reservations, jumping right into a training sequence. Within a few scenes she's being dropped behind enemy lines with a package for the French Resistance. She discovers quite abruptly that she's in over her head when she beseeches her first contact to help her find information on her boyfriend. The nervous operative is delayed just long enough to be arrested by the Vichy police and later executed.

Burdened by guilt and trapped in an occupied village, Charlotte is protected by local resistance fighters, falling in love with one of them as she helps hide Jewish children and blow up Nazi trains.

Her new love interest is played by Billy Crudup, who also has a track record of truly inspired performances ("Almost Famous," "Waking the Dead") that seems to hit quicksand in "Charlotte Gray." Aside from appearing convincingly gaunt and haggard -- having ardently struggled on the losing side of a difficult war of hit-and-run sabotage -- he's underwhelming as the soft-spoken resistance fighter.

Both leads are supposed to grapple with their feelings for each other, but their performances feel straightjacketed. There's no passion between them beyond the words they recite from their scripts.

Armstrong' ability to rattle the viewer occasionally surfaces in "Charlotte Gray" -- a scene in which her heroine gets on a train full of Nazi soldiers raises goosebumps. But overall her color palette makes a greater impact than any of the film's characters.

Far more memorable are the ways in which "Charlotte Gray" fails. It's emotionally vague. It never feels dangerous. It endears secondary characters (Crudup's father and two Jewish boys he protects) upon the audience but never follows up on them in the post-war coda. And the fact that nobody speaks French -- even though Charlotte's accent and use of the language is referenced several times -- becomes an awkward distraction from the story.

But for all its specific shortcomings, the biggest problem with "Charlotte Gray" (which was adapted from a novel by Sebastian Faulks) is simply that it doesn't make much of an impression. Armstrong fails to form an attachment to her characters. The movie revs its engine for two hours, but emotionally it's in neutral from beginning to end.

If the subject matter interests you -- the story of a woman joining the French resistance in the hopes of freeing the man she loves -- try renting the engrossing, exhausting 1999 French film "Lucie Aubrac." It's everything "Charlotte Gray" wants to be, and it's a true story to boot.