The second collaboration between German writer-director Tom Tykwer and his muse, actress Franka Potente, "The Princess and the Warrior" couldn't be a further departure from "Run Lola Run," the influential and groundbreaking piece of kinetic, adrenaline-fueled pop cinema that put them both on the map.

In that 1999 hit, Potente played a boyishly sexy post-modern alt-punk trying to save the life of her petty criminal boyfriend, who lost a cash delivery for his gangster boss. Set to Tykwer's own rave-styled soundtrack and edited to match, "Lola" followed Potente as she marathoned across Berlin seeking desperate last-minute solutions before the scheduled money drop. It's not quite an all-out assault on the senses, but it's nothing if not hyperactively energetic.

By contrast, "The Princess and the Warrior" is eerily serene, deliberately paced (135 minutes to "Lola's" 84), deeply reflective and intensely psychological.

Potente is almost unrecognizable in an incredibly visceral performance as Sissi, a meek, unstable, ingenuous woman-child who was raised by the staff at a psychiatric hospital after her mother, a resident nurse, was murdered by a patient when Sissi was a girl.

Now an attendant at the hospital herself, Sissi has little understanding of the outside world until a chance meeting with an emotionally scarred stranger awakens her heart to a whole universe of feelings she'd never known.

Hit by a truck while crossing an intersection, Sissi is close to suffocating from her injuries when Bodo (Benno Furmann), a shoplifter running from the police, dives under the same truck. He saves her life by performing a pocket knife tracheotomy, then disappears once she's safely transported to an emergency room, leaving her with nothing but a button she pulled off his jacket sleeve while clinging to him during the ordeal.

Haunted by the image of Bodo's stormy but stoic, tear-stained face that has roused a new sensuality, initiative and determination inside her, Sissi tracks Bodo to a run-down hillside shanty some months later (after a full recovery), only to find her hero a cruel, angry shell of a man.

Tykwer takes the time to burrow deep inside the damaged psyches of these two characters, as Sissi's perseverance eventually leads to a strangely romantic bond between them. The director provides flashes of the similar tragedies that shaped their lives (the deaths of Sissi's mother and Bodo's pretty young wife who was killed in a horrifying accident), and he gives his leads plenty of leeway to show how such troubled souls manifest themselves in the characters' personalities and physicality.

Potente's edge-of-instability performance plumbs Sissi's warped naivete and insecurity, embodying her with such a raw, apprehensive nature that she even walks with small, uncertain steps, like a child treading carefully on the thin ice of a frozen pond. Furmann is equally moving as Bodo, a man so wounded by his wife's death that he is at once both inhumanly placid and bursting with pain and rage. Tears roll down his cold, chiseled face at the slightest provocation, and he sleepwalks during nightmares, sometimes ending up on his knees with his arms wrapped tightly around a furnace he imagines to be the warm form of his dead wife.

But with all this going for it -- plus Tykwer's new, spellbindingly sedated style of meditating on the themes of chance, fate and love -- "The Princess and the Warrior" is walking on one wounded leg: It's underlying bank robbery plot often feels like little more than subterfuge.

Bodo, another of Tykwer's magnetic small time crooks, is planning a complex break-in at a bank where his cousin is a security guard. Sissi, of course, gets mixed up in the heist.

In the wake of the bank job, however, is where the picture really falls down. Their getaway feels in many ways like the end of the film, turning the entire last act into a clock-watching coda. Looking to hide out, Sissi and Bodo return to the asylum, where Tykwer launches a hole-riddled finale that depends on the absurd notion that a psychiatric hospital wouldn't keep any of its doors locked -- even those to inmates' rooms and stairwells that lead to the roof and even while the joint is supposedly locked down after an incident.

The tremendous performances and the film's engrossing, enveloping ambiance really take hold of you while watching "The Princess and the Warrior," but after the credits roll the nagging problems and logistical questions stay with you longer and more vividly than the story.