Cameron Diaz stars in 'The Invisible Circus'

In her place, in "The Invisible Circus," is a chain-smoking hippie terrorist whose every other word is four letters long, beginning with "f." Oh, and her character happens to be dead.

You don't buy it, you say? Well, good for you. You shouldn't.

Most of "The Invisible Circus" is downright ludicrous, although it does function as a decent European travelogue. If you're going to die a mysterious death, it may as well be on a cliff overlooking the sparkling, blue-green water of the Portuguese coast.

That's where quiet, insecure Phoebe O'Connor (Jordana Brewster) ends up after graduating from high school. The year is 1977, and she should be planning for college in the fall, but instead she's obsessed with the death of her free-spirited older sister Faith (Diaz) six years earlier.

Phoebe gathers the postcards Faith sent from her travels in Europe and follows the path her big sister took, hoping to find out what happened.

As Phoebe hops from city to city, we see Faith in flashbacks, smoking pot and taking part in political protests with her boyfriend, Wolf (Christopher Eccleston). In Paris, Phoebe tracks down Wolf, who is now engaged to a Frenchwoman and is no longer into that silly protest stuff. Reluctantly, he tags along on the trip and fills in some of the gaps.

For instance, no one knew Faith had joined a hardcore group of revolutionaries in Berlin, planting bombs and taking part in bank robberies.

(This is one of those hard-to-believe aspects of the film, in case you're wondering.)

Phoebe eventually finds the answers she seeks, but not before going on an acid trip and losing her virginity to Wolf, which is also ridiculous -- and unpleasant to watch.

Don't blame Brewster for this mess. She's perfectly adequate as a young woman on the brink of adulthood, and her transformation is believable, if not terribly interesting.

Blame the casting process; no one in this thing is a good fit. We've already talked about Diaz, who has been more believable in other dark roles ("Being John Malkovich"). Brewster is lovely but practically comatose, and Eccleston doesn't generate much heat either.

And blame the pacing. Writer-director Adam Brooks, who also wrote the screenplay for Oprah Winfrey's baffling adaptation of "Beloved," takes it so slow, he never creates a shred of suspense.

And the story behind the title, you ask? Well, Faith likes to invite mimes and clowns over to her house in the middle of the night to dance and cook eggs. How very ... forward thinking. Or something.

"The Invisible Circus," a Fine Line Features release that appeared at this year's Sundance Film Festival, is rated R for sexuality, language and drug content. Running time: 98 minutes.<