IN THE ROMANCING of the past, there is much falsehood. Yes, in years gone by, families slathered in sweat on a Washington summer's night would retreat to the parks in search of the slightest breeze. And yes, parents and children alike would settle onto a blanket and fall asleep under the stars. I have met many people who found respite in that way, and they speak of those nights on the grass at Hains Point or along Rock Creek with a misty nostalgia. I can only picture those nights in black and white.

Then -- for most Americans, sometime between 1965 and 1975 -- came air conditioning: a big bruiser of a window unit, perhaps, churning away in the living room, straining to ease a family's pain, or a modest machine in the bedroom, creating a cocoon of cool expressly for sleep. Blessed relief. If they didn't have to, people weren't about to toss and turn on a park lawn. So farewell to the parks, and to evenings on the front porch. And, if you accept the reasoning of the cultural historians who blame air conditioning for the decline of civility and community in this country, farewell to really knowing the neighbors and even to "the creative fury of the Southern writer," as one historian put it.

And now, the parks in the wee hours belong not to families and their neighbors, but -- well, who is out there? The other night, Sgt. Scott Fear of the U.S. Park Police took me along on the midnight shift. Fear spends his nights looking for sleepers, procreators and druggies -- all of whom are barred from the parks. Fear says night patrol is basically half sex, half drugs.

Rock Creek, Grove 14 -- popular for picnics by day, secluded for toking up at night. We find six teens drinking from 40-ounce beer bottles and smoking reefers made from Phillies Blunts cigars. The kids get a good scare and are sent on their way -- none of the officers on the scene actually saw them lighting up, so it would be hard to pin the drugs on any one kid. "They'll be back," an officer says.

On to Meridian Hill, the fantasy garden along 16th Street NW in the heart of the city. The park closes at midnight, but hours later, it is alive with bicyclists, clots of young immigrants in heated conversation, and dozens of young men in search of sex with each other. I walk up the hill alongside the burbling fountains and in less than 10 minutes, I am approached for sex four times. When three Park Police arrive on foot, some of the men scatter. But others ignore the cops. Bad move.

Two officers summon a couple of men walking together alongside a fountain. "We have a lot of problems with alternative lifestyle people in here at night," an officer tells them. The cops run the men's IDs, find no warrants, send them on their way.

But one of the men, both of whom are black, challenges the police, all of whom are white: "You didn't stop that white guy over there. You just told him the park closes at midnight."

"We were busy with you when we saw him," an officer replies.

"See up there, two more white guys," the stopped man says, pointing to some bike riders.

"Folks, park's closed," the officer calls out. "You gotta roll outta here, all right?"

The next guy the police stop is white, a nervous kid from Gaithersburg who has come to Meridian Hill "to find friends." "Where are they?" an officer asks.

"Um, Southeast, I think. I don't know streets. I'm just walking through here."

"Married?" No.

"Girlfriend?" Um, yeah.

Flustered, frightened, the kid stumbles over his words, contradicts himself a dozen times, suffers a very close body search, gets a lecture about being in a closed park and is dismissed. He scoots away in a flash.

Down at Dupont Circle, a park that never closes, more than 50 people sprawl across benches, lie on the grass, sit at the fountain, cluster around the eternal chess games. A man is out cold, splayed across the sidewalk, his face planted in the concrete. Two couples on separate benches are deep into activity that normally occurs indoors. Three winos share a roast beef sandwich.

Sgt. Fear moves along the benches, calling to the passed-out. "You okay?" The officer sees an old friend, Boyd Payne, a lively drunk who says he's been living in and around the circle for 28 years. They exchange stories about the good old nights, about drunks who once locked a rookie Park Police officer in the bathroom just off the circle, about a "bender" who borrowed a police horse and rode over to 17th Street to buy a pint. Lots of laughs, and an understanding. "I'm too old to go to jail now," says Payne, who's 50, but looks 60. He sometimes sleeps on benches here, but mostly finds nooks behind stores. It's safer there, he says.

The parks at night have become a no man's land. As we drive back through Rock Creek, we see raccoons, deer, a fox. It's their place now.

Marc Fisher's e-mail address is fisherm@washpost.com.