THE INVISIBLE CIRCUS. Drama. Starring Jordana Brewster, Cameron Diaz, Christopher Eccleston, Blythe Danner. Directed and written by Adam Brooks. (R. 98 minutes. At Bay Area theaters.)

Even at her most nihilistic, Cameron Diaz is about as menacing as a boozy college cheerleader. She can either beam with natural ebullience or go all glassy-eyed and belligerent, with few gradations in between.

Diaz's limited acting range, though, serves her just fine as a good girl turned baby terrorist in "The Invisible Circus." The dreamlike movie, based on the novel by former San Franciscan Jennifer Egan, is part beautifully shot European travelogue and part moving exploration of the darker side of the hippie era's rabid idealism.

Phoebe (Jordana Brewster) is a San Francisco teenager in 1977 still in shock over the death of her sister, Faith (Diaz), six years earlier. Unable to reconcile the loving, spirited sister she knew with the troubled creature who committed suicide in Portugal, Phoebe decides to retrace her sister's steps in Europe.

Phoebe finds Faith's old boyfriend, Wolf (Christopher Eccleston), in Paris. He accompanies Phoebe on her journey, and reveals, in flashback, how Faith's impulsive and reckless behavior escalated once the couple hit Europe.

The intense Eccleston ("Shallow Grave," "Jude"), sort of a more approachable Ralph Fiennes, is the glue of the picture. The steadiness and warmth in Eccleston's portrayal make it possible to see why both sisters would seek Wolf's stability. Like Diaz, Eccleston is a bit long in the tooth to be playing a post-teen hippie, but he is a good enough actor that age quickly becomes a non-issue.

Diaz shows her character's unraveling, but she also conveys her intense joy and love for her sister and father. The symbolically named Faith has been saddled with the broken dreams of her frustrated artist father, who then goes and dies on her. Flashback scenes with the father (Patrick Bergin) are introduced to help explain Faith's unstable behavior.

If only Brewster, who has the lead role, were as believable as Diaz and Eccleston. For starters, the dark-haired, olive-skinned Brewster ("The Faculty") is not in the genetic neighborhood of the fair-haired and blue-eyed Diaz and Blythe Danner, who plays their mother. Worse yet, she comes off as emotionally flat. Not damaged, but vacant. Her Phoebe is a perfectly pleasant girl who just can't be bothered to summon real emotion.

The scenery is another co-star of the film. Europe looks scrumptious, aided by long shots of sun-dappled coastal highways. In the same vein, the three principals also look beautiful, especially Diaz, whose character manages to keep an extensive wardrobe of diaphanous hippie wear and chic revolutionary gear despite her itinerant lifestyle.

"The Invisible Circus" shows the personal and family instability that existed during a tumultuous time. It manages to be both a paean to the era and a cautionary tale. The scenes of free-flowing, lovable San Francisco eccentrics and gorgeous European vistas seem to promote tuning in, turning on and dropping out. At the same time, the story debunks the notion that this was the easier path.

Advisory: This film contains sex, nudity and violence.