Uh-oh. They’ve Found Us.

In 2003, after his Southampton share fell through, author John Blesso found himself in Kismet, Fire Island’s westernmost hamlet. It was his first visit, but the car-free streets and the relatively modest prices persuaded him to forgo places like Water Mill and Sag Harbor. “I realized, even if you’re not interested in the red-velvet-rope scene, you’re still paying for it,” he says. In Kismet, he found a six-bedroom house a few steps from the ocean for an un-Hamptonish $585,000.

Nothing lasts forever, of course, and now there’s a fresh sign that deals like that may be a thing of the past. This year, the behemoth brokerage firm Prudential Douglas Elliman has opened a branch office on the island, in Cherry Grove. It’s the first of the big New York firms to do so, and it’s a sign that Fire Island’s quiet days may be coming to an end. (Citarella, the fancy grocer, is rumored to be opening a branch there, too.) “It’s totally undervalued,” says Elliman president Dottie Herman. Though towns like Point o’ Woods and Saltaire do have million-dollar homes, they’re the very top of the range; in East Hampton or Nantucket, that’s the bottom. CJ Mingolelli, who’s heading the new office, says 60 percent of clients who’ve called about rentals or sales this spring have been newcomers. “There are [deals] to be had,” he declares, sounding rather like a Manhattanite who’s eyeing a place in Prospect Heights. There may be, but not if this keeps up: A big house in the Pines just rented for $100,000 for August—far and away the most ever.

Fire Island devotees have always seen it as a better, less-sceney alternative to the South Fork, and they’ve been largely left to their own devices: Apart from the long-established gay men’s scene in the Pines and the Grove, New Yorkers have been slow to bargain-hunt here. As a result, the business of realty is extremely low-key. Some local offices don’t even have Websites, relying on repeat business. “The people who really want the Hamptons aren’t happy here,” says longtime island broker Linda Cahill. “We don’t have the glitz.” That’s likely to change with Elliman’s powerhouse marketing machine. “I’m sure prices will skyrocket,” predicts Simone Weissman, who’s summered in Fair Harbor for two decades. “I’ve seen lots of turnover, and people are leaving.” This summer, one of her neighbors couldn’t return to his usual rental after 27 summers there, having been priced out. “It’s a shame,” she says.

Uh-oh. They’ve Found Us.