Will Meredith Choose McDreamy or McVet?

For a medical drama built around a group of hyper-self-aware, high-achieving surgical interns in a Seattle-area hospital, Grey's Anatomy is anything but brain surgery. In fact the only question on the minds of millions of devoted viewers of ABC's breakout hit, which has its third season premiere Thursday at 9 p.m., has nothing to do with medicine or science and everything to do with chemistry — the romantic kind. Whether they are high-school girls experiencing their first big crush or their mothers relishing a good nighttime soap — hordes of whom watch the show together as a mother-daughter bonding ritual — fans of the show all want to know whom surgical intern Meredith (Ellen Pompeo) will pick as her lover, McDreamy or McVet?

McDreamy, in case you haven't heard, is the nickname for Dr. Derek Shepherd (Patrick Demsey), the handsome, married neurosurgeon who broke intern Meredith Grey's heart. Finn (Chris O'Donnell), aka McVet, is a shaggy-haired veterinarian she's been dating to get over McDreamy. In the season finale of the show Drs. Shepherd and Grey unleashed their passion in an exam room of Seattle Grace Hospital. Now McDreamy wants her back. Or does he? And whom will Meredith choose? Producers have been frustratingly mum on the subject. "In the season premiere a relationship will end but it's not the one you think," executive producer Betsy Beers told TIME.

Like everyone involved with the show, Beers knows how to milk the guessing game, reminiscent of the Dallas "Who Shot J.R." cliffhanger 26 years ago, for all it's worth. Disney/ABC'S marketing department has used on-air promos constantly, along with two-hours of reruns on Thursday nights, free downloads on iTunes and sneak peeks in a four-minute music video, "How To Save A Life," by The Flay. To top it off, ABC released the second season's DVD set and soundtrack last week — all amping up the frenzy in the final stretch.

But a grassroots frenzy like Grey's Anatomy's can't be entirely manufactured. What started as an iffy mid-season replacement in 2005 has turned into a monster hit for ABC with a fiercely devoted following, the majority of whom are women. Last season Grey's was the highest-rated 10 p.m. show on any network and the second-highest-rated drama among the coveted 18-to-49 demo, second only to Lost. McDreamy's picture is plastered on school lockers, cell phones, screen savers and even cubicle walls. "There aren't many characters like him on TV," says Robert Thompson, professor of television and popular culture at Syracuse University. "He's not only a Prince Charming, and a doctor, but he's more complex than a lot of men on television." Sums up Beers: "He's phenomenally appealing for a brain surgeon."

In addition to McDreamy, older women tune in to Grey's Anatomy for its rich cast of characters, riveting storylines and quirky medical cases (a writer who swallows his first novel, a pregnant cancer patient who rejects chemo in order to have a healthy baby, a woman "suffering" from uncontrollable orgasms). Unlike edgier high-concept hits such as 24 and Lost, Grey's harkens back to TV's conventional medical dramas, including St. Elsewhere and E.R. — topped with a hefty dose of sex to keep up with the times. At a time when TV is also overflowing with either unscripted reality programming or shows dealing in danger, terrorism and uncertainty that mirror the real world, the problems of five surgical interns and their bosses at Seattle Grace seem refreshingly familiar. "This is an old-fashioned show, and that's what makes it feel fresh," says creator and executive producer Shonda Rhimes, a black woman who has made a conscious effort to increase diversity (both racial and gender) in the show's casting. "The high-tech plot-driven shows are fantastically exciting. We're an alternative." And unlike Meredith's dilemma, there's no uncertainty about which option viewers of Grey's Anatomy will choose.