They remember what it was like to be afraid to walk into their apartment building, afraid of being mugged in the elevator or the basement. And the people who live at 1760 Euclid St. NW say they fear that those times may return if the U.S. Immigration and Naturalization Service forces Silbert Anderson to leave the United States.

Before Anderson became resident manager three years ago that was the way it was: a dirty building haunted by violence. Now the halls are pristine, the basement -- once a fetid dump populated at night by winos and bums -- has a laundry room and freshly painted floors.

The tenants and Anderson's employers at the William C. Smith Co. say he almost singlehandedly is responsible for the transformation.

But Anderson is an illegal alien, a Jamaican, who, according to the immrigration service, has no rigt to live in the United States. Unless the service changes its mind he will have to leave the country by tomorrow.

Scores of people who live in the building and who know Anderson in the Adams-Morgan community have written letters attesting to his character in an effort to sway the immigration service. They call him reliable, hardworking and courteous. "We all love him very much and would hate to see him go," one said.

Rebecca Kite, a retired Justice Department librarian who has lived in the building 30 years, said Anderson has helped her around her apartment and has done her shopping for her ever since "suddenly... I got old. If he goes back (to Jamaica) I don't know what I'd do. If he goes back I'll have to go to a nursing home."

INS District Director Joseph Mongiello says he has studied all the evidence and the departure of Anderson is virtually inevitable; to grant an extension, Mongiello says, would only delay that departure.

If Anderson is allowed to stay simply because he has done a good job and his tenants love him, Mongiello said, "I can guarantee you every apartment building in the city will have an illegal alien working like crazy."

Anderson is "trying to make it an issue as to whether he is of good moral character," Mongiello said, and that, he said, is not sufficient grounds for keeping Anderson here

Anderson, sitting with his 6-year-old son and his fiancee in their apartment, spoke quietly, in the fluid tones of the Caribbean. "I've been going through something," he said, "that I never know I'd be able to go through.... I wouldn't say the United States has treated me bad. It's just for a mistake I made that I'm paying now."

The story of how Silbert Anderson came to the United States and why he may be forced to leave now is a chronicle of personal misjudgments, deceit and jealousy all in the context of federal immigration laws.

Basically, the 33-year-old Anderson says that he only planned to visit this country for a week. But the woman he came to see, he says, hid his passport from him and persuaded him that the only way he could return to Jamaica and keep from getting locked up was to marry her. He did.

When they had a violent fight about another woman a year later, she turned his passport in to federal officials and told them he had bought a gun.

Anderson was convicted of what U.S. District Court Judge Oliver Gasch called "the very technical offense" of owning a gun while living in the United States illegally, and was given two years' probation.

His wife, Norma Marion Brown Anderson, could not be reached for comment last week.

One senior INS official, asked his opinion of Anderson's account, said with a touch of exasperation, "This is a crazy story."

Anderson's employers, his tenants and his friends in the community have stood beside him, however. One letter to immigration from a group of eight tenants said Anderson is "very reliable, dependable and always very courteous." The last three words were underlined.

At Anderson's deportation hearing last year, two tenants, Anderson's supervisor and the supervisor's wife, all testified on his behalf.

Even Anderson's probation officer appeared to be won over at the deportation hearing. "I believe him, you know," he said without further elaboration.

None of this has affected his situation with the Immigration Service. Anderson was ordered deported last year. The Board of Immigration Appeals overturned the decision eventually to allow Anderson to leave voluntarily, thus making it somewhat easier for him to reenter the United States, but he still was given only 30 days to leave.

Anderson's lawyers, David Goren and Michael Maggio, now are fighting for a decision by Mongiello to extend the period of time Anderson can stay here, possibly for as long as seven months.

That would allow Anderson's little boy (the offspring from an earlier relationship in Jamaica) to finish the school year at Marie Reed Learning Center, and enable Anderson to complete his divorce from Norma. He says he is in love with an American woman. He has said she will marry him, and thus enable him to stay here legally.

Under the law, Mongiello has the authority to permit all this on the basis of "compelling humanitarian concerns," but he says he has not found any.

Anderson's lawyers say if he goes back to Jamaica now it could be two years or more before he can get a divorce and begin to straighten out his life, much less return to Washington. His employers and his tenants say they will be waiting for him.