The road not taken, the door unopened, the door that is opened, the decision - conscious, or not - to turn left instead of right.

What would happen? Whom might we meet? Could our life have taken a different course?

In the small, unsettling Another World - a low-fi indie that started a high-profile bidding war at Sundance this year - these big questions are investigated, in resonant, suspenseful ways.

Another Earth centers on an MIT astrophysics major, Rhoda (Brit Marling), who leaves a party one night, inebriated, drives through an intersection, and crashes into a minivan, killing all but one of its occupants. She was distracted by a strange sight in the sky: a planet, much like ours, hanging there, as if someone had held a giant mirror up in outer space.

Four years later, released from prison, the promise and possibility of a brilliant career derailed, she seeks out the survivor of the crash: a composer, John Burroughs (William Mapother), whose family she destroyed.

Rhoda doesn't let on who she is, and Burroughs, depressed and isolated, doesn't know the identity of the driver who killed his wife and child. And so they meet - she says she's with a cleaning service, his house is a mess - and meet again. A friendship is formed. The musician, middle-aged and alone, falls for the attractive young woman. And vice versa. Like the old Neil Young song goes, a man needs a maid.

One of the smart, effective things about Another Earth is that it treats the discovery of a parallel planet in, excuse the pun, a down-to-earth manner. The movie's sci-fi elements are the stuff of the TV news, the newspapers, the Internet. The doppelgänger orb looming in our solar system becomes something almost taken for granted.

The real drama here is the relationship between Rhoda and Burroughs - and the gaping void where the truth lies. Eventually, he's going to have to know.

Marling, in a nicely calibrated performance, projects sadness, and quietude, and the glimmer of hope. Mapother seems less certain in his role - grief and pain are hard things to play down - and the script isn't always that sharply honed. But he's convincing, compelling.

Another Earth has heft - emotionally, intellectually. Like the image of the Earth floating out there, pasted to the heavens, this fine film stays with you, follows you home.EndText

Contact movie critic Steven Rea at 215-854-5629 or srea@phillynews.com. Read his blog, "On Movies Online," at http://www.philly.com/philly/blogs/onmovies/