PARK CITY, Utah  – The cinema world may one day give much thanks to the anthropology department of Georgetown University.

While studying there, Zai Batmanglij met Brit Marling and Mike Cahill and together they began making short films. Cahill and Marling are responsible for the first major discovery of Sundance 2011, the astonishing sci-fi piece "Another Earth." Now Batmanglij and Marling deliver another terrific and engrossing venture into speculative fiction, "Sound of My Voice."

Marling stars in both films as well as being their co-writer and co-producer. Each displays an inventive story line with believable characters caught up in extraordinary events where tension builds with each successive scene. And each ends abruptly with an ambiguous ending that delivers one of those ah-ha moments.

Batmanglij, an AFI grad making his first feature, has developed a story with Marling that requires production ingenuity rather than big bucks or a large cast. It deals with a subject that's hardly new to film, that of cults and their mysterious leaders, but does so with a fresh viewpoint and intriguing possibilities.

A Los Angeles couple, Peter (Christopher Denham) and Lorna (Nicole Vicius), infiltrates a San Fernando Valley-based cult with the idea of making a documentary expose of its charlatan leader. But the leader winds up scrambling all their expectations.

Some time before, one follower found a young woman, Maggie (Marling), wandering downtown in a dazed and physically compromised state. Rescued and nurtured back to health, Maggie now claims to have come from the future, from 2054, in fact. She gathers around her disciples who can benefit from her foreknowledge of a coming civil war.

Since she is allergic to most things in the present day, she doesn't venture from a basement chamber and needs frequent blood transfusions and organic food grown obsessively by her followers.

As the newcomers get initiated into the small group, Maggie achieves an emotional breakthrough with Peter involving his troubled past. While this shakes him up, he maintains his cynicism but Lorna has her doubts -- about his cynicism. She suspects he is hooked on the leader in more ways than one.

There are ominous signs everywhere about Maggie's intentions. She insists her followers learn to subsist on foraged food. Another true believer (a cajoling Kandice Stroh) takes Lorna deep into a wooded area for target practice. Then Maggie demands that Peter bring a specific little girl to her.

The film is deliberately sketchy and impressionistic. You get snatches of backstory about the two infiltrators and Maggie relates her own story, to be believed or not. The actual intent of the cult and Maggie's plans remain hidden. What is clear is that the filmmakers are not going accept the couple's cynicism. Instead they raise the possibility that Maggie just may be telling the truth.

After all, audiences believed in all the time travel in three Terminator movies. So why not in a low-budget indie even if it contains not one scrap of sci-fi razzle-dazzle? Everything in this film is totally realistic. So the filmmakers slyly leave it up to their audience to determine what the film is actually about -- a time traveler or a dangerous impostor?

This is speculative fiction that goes a step or two beyond "The Twilight Zone." It's not reality stood on its head by surreal events but rather a reality where not all is seen or revealed, where other realities may exist.

A music score promotes a worrying mood but does so at higher decibels than necessary. Other tech credits are very good for what is clearly a super low budget.