SOMETIMES IT FEELS like film has collapsed into cliché. We've seen every exploration of the misanthropic human condition, each ridiculous Romeo and Juliet romance, every satire of society. But filmmaker Marc Singer has found a way to be jarringly unique: self-sacrifice.

Singer spent two years living on and off in the railroad tunnels of New York City, learning about the subculture of homeless people who build their own "houses" there (shacks assembled from old wood and steel scavenged from dumpsters). There were 50 to 75 people living underground in the winter, and twice that in the summer; they have electricity (illegally tapped from above), primitive alarm systems, makeshift stoves and showers, and watchdogs.

Singer does a remarkable job probing the lives of these people to uncover the gritty, horrific reality of their daily existence. Everything is shot in musty, eerie black and white and scored with an ethereal soundtrack from DJ Shadow.

But there's more to the film than cinematography. Writing about The Oppressed can be dangerous, and Singer's not patronizing. Though he definitely invokes empathy, he evaluates his subjects as people, and he challenges them by asking them why they're there and what they plan to do in the future. Over the time he lives there, they become his friends.

There's Dee, who's a drug addict. In addition to some incredibly haunting images of Dee mindlessly smoking crack, Singer nonchalantly flashes between scenes showing her quietly weeping while she describes the death of her two children--they burned to death, and she saw it on the news from prison--and domestic shots of her laughing while cooking food with Ralph, her neighbor.

There are five other characters, and each teach you something new about the culture of the underground homeless. Tommy is 22, he collects $70 worth of cans a day, and built a room for his three dogs in his two-story suite. And there's Ralph, Dee's friend, who is five years off crack, and perhaps the cleanest member of the community. At the time the film was made, Ralph had been living in the tunnel for three years, and his house is one of the most sophisticated.

The material of this documentary guarantees an interesting film. But what makes it really great, is Singer's simplicity. He doesn't use it to push his social message towards the audience. He's not a communist, not a hippie, not trying to solve the homeless problem throughout the world. He's a middle-class British kid who met these people after moving to the East Village from Miami, and his first goal was to make enough money from the film in order to pay to house everyone living in the tunnels.

He also worked independently of the rest of the film world. He'd never even picked up a camera before he started shooting. Instead of enlisting other filmmakers, his subjects became his collaborators. He ran wires through the tunnels, set up cameras, and paid his subjects, who are all identified in the credits by their first names.

The only real problem with Dark Days is the end, where Singer loses sight of the best part of the film. In his efforts to get the people real homes, he starts investigating the Amtrak officials' efforts to evict them and the federal government's welfare system. He ends up wrapping it all up into a sugar-coated, sappy ending, one that doesn't even begin to address the issue that he's brought up all of a sudden: the magnitude of the homeless problem in America, the prejudices against them, how they are lost in a bureaucratic nightmare. Singer would have been better off had he stayed focused on profiling individuals, rather than wandering into the world of addressing political and social change.

Even so, the film will undoubtedly linger in your mind for weeks afterwards. You will have no choice but to thank Singer for sacrificing his own comfort in order to make you a voyeur in a world that no one else is willing to really face.