"THE Galapagos Affair: When Satan Came to Eden" is a story ripped from the headlines, although this mystery has been around for close to a century. The documentary looks at three groups of settlers who landed on a previously uninhabited island in the 1920s and '30s. Two disappeared and two others ended up dead, and if the volatile relationships between the settlers are any indication, foul play easily could have been involved.

In 1929, a Nietzsche-obsessed doctor, Friedrich Ritter, left his wife and his German homeland to flee with his mistress, Dore Strauch, to Floreana, a deserted island in the Galapagos archipelago off the coast of Ecuador. The pair of humorless vegetarians had become disillusioned with society's constraints and obsession with wealth, so living off the land far away from civilization seemed like the right antidote.

But news articles about the couple's escape gave other eccentrics the idea to follow. Ritter and Strauch were not amused when the German Wittmer family - Heinz, Margret (five months pregnant at the time) and their young son - crashed the couple's private party. The misanthropic Ritter was especially annoyed, and even told Margret that he would offer no medical assistance in the case of complications during childbirth. (To his credit, he did end up helping, but that appears to have been his only redeeming moment.)

The Wittmers, who wanted to live like the Swiss Family Robinson, were in turn highly agitated about the arrival of another group led by an exhibitionist, self-proclaimed Viennese baroness, Eloise Von Wagner. She brought along not only her two lovers but plenty of media attention with her habit of dreaming up outrageous stories about herself and her neighbors on the island, which she fed to reporters.

She and one of her companions disappeared without a trace months later, and it wouldn't be a reach to say that any one of five co-habitants could have been responsible.

Writers and directors Daniel Geller and Dayna Goldfine have pieced together the intersecting lives of the three groups with a healthy stockpile of letters (read by the likes of Cate Blanchett, Diane Kruger and Josh Radnor), video and photographs.

"The Galapagos Affair" spins a strange and compelling tale, with perfectly sinister music by Laura Karpman setting the mood. But the movie is better at building suspense than following through. It isn't entirely clear until late in the film who disappeared, who died and who might have been responsible, and that sense of mystery turns out to be an effective device. Yet when those details are revealed, the result feels anticlimactic.

That is due largely to an excessive run time of two hours but also to the unnecessary focus on the former and current inhabitants of other islands in the Galapagos. The directors want to offer some context for why people might move to deserted islands and what it's like to grow up on one, but the interviews are hardly revelatory; these people were running away from society; their sons and daughters grew up feeling isolated.

The most fruitful interviews are with Ritter's grand-nephew. He gets the final and most memorable words: "If you are the problem, you can go wherever you want and you'll still have problems."

If "The Galapagos Affair" had stuck to that theme alone, it might have been more than intermittently intriguing.