Irony, sadness and tragedy have a peculiar way of melding sometimes. The other day I received a telephone call from a woman I know, a resident of the Adams-Morgan area. She had seen my column titled "Everybody's Business," which dealt with the emerging hard-drug underworld in the District of Columbia. She told me a tale that set me to pondering and to asking myself what, indeed, is the world coming to?

She lives on Fuller Street NW, which contains two foreign embassies and a nice middle-class apartment building on one block, and an overcrowded ghetto on an adjacent block, a somewhat common phenomenon in Adams-Morgan, an ethnic melting pot where haves and have-nots live in juxtaposition.

Once, according to my caller, restless people milled about the poverty-stricken block: bored, unemployed teen-agers vandalized cars, arguments sprang up as suddenly as spring rains, and a woman walking down the street could be met with hostility if she didn't return a risque greeting with a smile.

Some of the harassed "haves" would not walk the block between Mozart Place and 17th Street; others, recognizing the reasons behind their neighbors' behavior, made friends with them in an uneasy truce.

"It was not dangerous," my caller said, "but it was terribly obvious that people did not have the money they needed to live; that they did not have as much as the people on my block and around the corner."

But about two years ago, everything changed. A dope dealership began operating in the depressed block.

These drug dealerships, according to District police, are makeshift clusters of dealers and hierarchies of friends, acquaintances and others who operate as crime captains, lieutenants, sergeants and crew members.

It was the lowest rung of workers in this business that the residents of the middle-class block of Fuller watched in horrified fascination.

The youths, the crew members, worked the street in regular shifts. Customers would drive through and roll down their windows, and one of the youths would come out to the curb and sell them dope.

This activity produced an amazing result. People began to have a little money to spend. The young peoples' restlessness, tension and resentfulness diminished. They began to speak more politely to passers-by on the street.

Petty vandalism to automobiles declined. The professional people who lived in the well-kept apartment building didn't have to worry anymore about litter being dumped in front of their building.

"Except for the occasional police raid," my caller said, "the block got quiet."

The drug activity even transformed some of the youths into apprentices of the Protestant work ethic as their crime captains and sergeants lectured them on reponsibility and trustworthiness.

My caller recalled a scene where a lieutenant in his late twenties was lecturing a younger dealer about how to properly conduct business.

"He was using the kinds of terms you would hear in the classroom or in a locker room where a coach encourages his team -- good American stuff about responsibility and making sure people were able to trust you."

As the drug trafficker spoke, a group that included children from nearby H.D. Cooke Elementary School stood and listened.

My caller was struck by a sad irony: As Washington's street heroin markets have spread, drug dealers, bringing money from their big profits to poor inner-city blocks, are being seen as heroes, just as rural South Americans view vicious cocaine traffickers as Robin Hoods spreading wealth.

"This," said my caller, "is going to be the most successful, efficient enterprise they see black people engaging in -- selling dope."

Pondering that call, I was struck by the tragic fact that it is the dope dealers, soliciting peons in the service of the deadly domain of heroin, who have brought the most order, money and motivation into that little world.

The further irony is that while Washington is a town with many positive black role models, it also is a town where communities are deeply divided and people live side by side, but in isolation.

My caller's point was obvious: The absence of work had devastated that block. People need work not only to make money to live, but also to gain self-esteem and identity. They need to be able to do it within a legal system.

As my caller put it: "It is tragic that it's dope that is doing it. It shouldn't be the dope . . . "