[Permanent disclosure: Any and all TV shows or films discussed here will inevitably contain minor spoilers. Deal.] I think it was the moment when Leoben the Cylon revealed to Starbuck that her excised ovary had been salvaged and used to create a human/cyborg daughter that I began to understand that "Battlestar Galactica" is one dark, sad show. The sci-fi drama's third season kicked off in high gear on Friday, picking up after last season's cliffhanger pretty much imploded the show's universe by jumping forward a year to show the struggle of the human settlers on New Caprica and the return of the Cylons, who invaded the fledgling colony and established their own rules. The show is simply amazing. It's nothing new for a series to walk the line between light and dark; ever since "The Sopranos" bowed in 1999, darkness has been in vogue, especially on cable, with "Deadwood," "The Wire," "Rescue Me," "Nip/Tuck," and "The Shield" going all-out to show the inner horrors of the human psyche as their characters fell to impossible depths of loneliness and depravity. But "Battlestar Galactica" is different from most of those shows because it features likable, relatable characters, whereas most of the other series are just crazy for the sake of being crazy. Take "Nip/Tuck." It's a visually stimulating show, but absolutely pointless. It does dark better than most — Sean's recent drug-fueled hallucination of his personal demon banging his personal angel was attention-getting, to say the least — but the darkness isn't tempered by any kind of genuine emotion. It's not that I want the show to be lighter; I want it to make me care about the characters who are dealing with such hard, dark times. And I don't. Sean is a whiny punk, his wife is a bitter wreck, and Christian is a soulless husk of a man who sees the futility of his ways and doesn't so much refuse to atone as much as he just lets thoughts of atonement drift away like a bad hangover. Let them suffer. Conversely, the rough road that the denizens of the "Battlestar" universe walk is heartbreaking precisely because the writers, producers, and actors put so much energy into making me care for the characters. The stunning casualness with with Col. Tigh loses an eye serves to underscore the colonists' dire straits, reinforce the image of the Cylons' murderous ways, and instill sympathy for Tigh all at once. The show isn't in a rush to show how dark and crazy it can be, as in the story line on last season's "Rescue Me" when it seemed like everybody was raping everybody just for the hell of it. And "Battlestar" stands in dark contrast to Showtime's new series "Dexter," which is so busy trying to look cool you forget that it doesn't matter who lives or dies; you just don't care. So many shows are wallowing in pointless vice without having it smack up against virtue, which is what creates genuine conflict and memorable relationships for a series' characters. The physical violation of Starbuck is that much more horrifying because we've already come to identify with her and relate to her, to sympathize with her struggle to balance the coldness that keeps her alive and the love (lately for Anders) that keeps her going. Tigh isn't some cartoon villain, but a man who wants to do right and has a blind spot a mile wide for Ellen, his duplicitous wife, and the series even tempers her acts of betrayal with emotion: She does what she does to save her husband from the Cylons. The plots develop from the spark between people's basest interests and purest intentions, making the darkness something we recognize as our own.