The street is dark. On the list of buzzer numbers, next to the glass double doors and under the blue awning of the tall office complex there is no mention of the agency. The hallway inside is empty and dirty. A very loud, very slow elevator goes up to the seventh floor, where through an open doorway there comes a low voice, its intonation practiced, though scarred by cigarettes. I am here for an unusual kind of job interview -- this is an escort service, and I am pretending to be an aspiring escort.

-In her office, the owner Karen* is making dates, dispersing her employees throughout Philadelphia. I hear her sending a girl to a "regular" near Broad and Locust, instructing another to count out the cash she's just received. I hear her describing a girl named Lee* to an interested caller -- 36C, 24, 36. They're at the Double Tree, the Hilton and private residences.

Karen's waiting room is a simple office space masquerading as a country club powder room -- large gold-painted mirrors, framed prints of Romance paintings and tall topiaries covered in plastic ivy contrast the false panel ceilings an neon lighting. Wooden figurines of cows and pigs cover brown metal desks. There are boxes of tissue everywhere, fanned copies of Elle, Ladies' Home Journal and Better Home. This is where the girls sit and read and wait.

Karen knows my height and weight and that I consider myself "attractive." She does not know that I'm a fake. She's asked me to do my hair and make-up, but to dress normally, a sweater and a pair of jeans.

I am here under these false pretenses to ask the question that no one on the inside of the escorting business will answer for anyone on the outside. Only the clients and the girls will get a straight answer -- is this sex in exchange for money?

Is this prostitution?

In Karen's office she lights a Merit cigarette and fusses over her new telephone. She is 45 and still beautiful -- an escort since her early 20s. And she levels with me very quickly.

Am I expected to have sex? I ask.

Yes. Tip is included in the hourly rate, $250, so my clients will be expecting me to. I would go and make pleasant conversation, and wait for a cue -- an invitation to get more comfortable perhaps, or a seat on the bed. But it's so fast, she says. She assures me premature ejaculation is common, that most of the hour is spent talking. They're so nervous, she tells me. Her voice is very kind.

She claims her clientele to be the shy and the nervous, the insecure but financially secure. The cr?me de la cr?me as far as the escort business goes.

These men want someone to make them feel interesting, desired. Most are single, tired of the bar scene, and looking for a convenient alternative -- and they want it quiet. Professional escorts don't arrive at the hotels in fishnets and tube tops, but in jeans and sweaters. Discretion is the service's highest priority. I'll be safe, she assures me. I'll be incredibly well paid. It's like being a waitress. By the end of the night, I won't even remember who I was with.

And that's how Karen thinks it should be, unless -- for some reason -- I had a really good time. Because, like in any work place, sometimes people fall in love. The men get attached, and girls have married their clients. Karen considers one of her past clients to be the love of her life.

I glance at her left hand and there's no ring.

Before I go, she advises I just dive right in. She tells me I'll be so busy counting my money. Again and again, she repeats, I won't even remember who I was with.

In the back of any weekly newspaper, under 'escort' or 'massage' in any yellow pages, there are around 60 or so phone numbers that can turn any ordinary night into a one night stand. For the busy, the bored, the lonely, the horny, these services promise models, dancers, athletes, college girls, fetish lovers, geishas and masseuses, or they call them sweethearts, angels, sophisticates. They can't be found on any street corner. Instead, Candy, Roxy, Trixie, Jessica, Adrianna are on the Internet or in print -- a phone call and a trip to the ATM away. They are "dates," -- an hour long goes for anywhere from $100 to $400. The phenomena's existence relies on a flair for secrecy, for deftly exploiting the loophole in Pennsylvania law. For denying the very things that Karen told me in her office. Sex for money is happening behind the closed doors of hotels and homes all over Philadelphia, accessed by ads in the wide open.

Surprise -- academia is not exempt. Our own Penn boys are doing it. Though they may be less comfortable than an older man might be with the world of sex workers and though they may have more options -- binge drinking and liberal sexual policies being characteristic of university life -- some of these entirely forgettable men Karen described are students.

Tom* is a senior Penn student with a small cache of friends who say they've shelled out for sexual favors. They are, like most Penn boys, involved, out-going They like to party, they like sex. They are neither socially inept nor starved for female attention.

"They have good game," Tom says. "Some of them hook up with pretty attractive girls."

The appeal often seems to be alcohol induced -- just a late night and a crazy notion. Intercourse with an escort is not particularly common; more than likely they'll receive oral sex or a handjob. Penn kids are known frequenters of massage parlors in Center City, the in-call side of many escort services.

Escorts can also be hired as strippers for parties. In either case, an opportunity for sexual favors usually presents itself.

"They're drunk, they go there ... They massage you a little bit, than they flip you over and jerk you off," Tom explains. The client rarely has to imply.

"It's kind of an adventure. But mostly it's just biology takes over with these kids. The guys that do it don't have high taste at all -- they have no taste. That's not an issue with them."

Most Penn students are more risk-adverse, Tom speculates. Escort users aren't rampant. Because quite clearly, this is prostitution, made legal by carefully exploited technicalities. Made successful by what is implied.

Just for the record, I wasn't trying to sell sex," says Anton*, the former owner of G.I.P. (Get It Poppin') Entertainment, "You're not arranging for sex, you're arranging to have a date."

This kind of explanation is what keeps escort work legal, a claim echoed by each and every escort service -- they are dating services, not sex services. Though the ads in the back of the weeklies feature buxom blondes in thongs, there is no guarantee that you'll see whoever arrives at your door that way.

Escorts are, by law, only dates. What happens behind closed doors is meant to be a personal decision -- a decision made by two consenting adults based on chemistry. Nevertheless, the high price tag has sure implications.

Despite this cautious explanation, G.I.P. folded after only a brief period of operation when Anton and his partner became nervous about getting in trouble with the police. His employees, a handful of decent looking girls in their 20s and 30s, disbanded, and Anton speaks candidly on why they wanted to work for him.

"The girls -- they knew what was up. There was really nothing that needed to be said. Girls that want to do, like, freaky, nasty shit for money are a dime a dozen. It's a shame because it's somebody's daughter, but, y'know ..." says Anton.

Anton is like many escort service owners. Quiet about what his girls will do -- he constructed more of a "don't ask, don't tell" policy with his employees than someone like Karen -- but without any moral qualms over the exchange of money for sex.

"As far as I'm concerned, prostitution should be one-hundred percent legal," he says, "Y'know, there's not much of a difference. You give somebody a massage or you give them a hand job -- pleasure is pleasure."

But this stuff isn't legal. Even though it may be a freaky girl's choice, though it may be an adventure for Penn parlor users, though Karen and her girls are cool and relaxed with their harmless clientele -- and even though everyone is doing their best to keep their mouths shut about it -- it is the Philly police's job to put everybody out of business.

Lieutenant Charles Green and the City Wide Vice Unit takes complaints -- wives who've noticed mysterious credit card charges, neighborhood-watch groups and even dissatisfied clients -- and respond, often with undercover operations. The cops on vice will call for a date and arrange to meet at a local hotel -- while being very careful not to raise any re-d flags for ultra-cautious escort service workers. The service will reject a suspicious-sounding caller and are keen to the descriptions of certain officers.

"We'll say, I'm looking for a nice lookin', tall, red headed girl," explains Green. "They'll send in the red head, and they'll say, okay, it'll be $150. We say, well, what am I getting for $150. She'll say, whatever, without spelling it out for you, or she'll say half and half, oral and intercourse."

If a deal is made, the girl is busted. Once it has been made clear that the red head is offering sex for money, she's off to jail for the night. Sometimes, it doesn't go as well.

"It's a pretty neat service. 'They're already guaranteed $150,' she can say, 'this is all I'm going to do, your hour is up.'"

Even though most of the time the girls will make the mistake of spelling it out for the officers, the punishment is hardly life shattering. The girls go to jail for anywhere between 12 to 36 hours, depending on how crowded the jail is that night.

"This is not a violent crime, and courts -- they don't get harshly dealt with."

The punishment is often probation, community service or substance abuse rehabilitation, if drugs are involved. After a few of their girls get busted, a service will pack up, disappear, only to resurface under a different name and with a different phone number. Vice has busted massage parlors, brothels, escort services and S&M houses, but their powers of regeneration are clear to him.

The Lieutenant asks me to describe Karen, who claims never to have had problems with the police before.

"I more than likely know who it is," Green says.

They're hard to bust and impossible to eradicate. The whole cast of characters -- the escorts, escort service owners, clients and police are all doing a funny kind of dance around one another -- the clients don't want to be ripped off, the escorts don't want to get caught, the police can't seem to stop them, the owners don't want to get shut down. An incredible amount of money is changing hands, available to the people willing to shoulder the risk.

And there's always somebody. They're there, 24 hours a day, seven days a week.

There's always somebody. Waiting to take your call.

* Names have been changed.