They sat there, three diminutive and worried Mexican women, in the shadows in the back pews of St. Jerome's Church in the Bronx. Father John O. Grange noticed and motioned them forward.

The women handed Grange a letter. They had asked for apartment repairs, and this letter contained what appeared to be the landlord's response.

"Dear Tenants," the letter stated, "As you know the United States Government and specifically the Homeland Security Administration is investigating illegal aliens . . . I have given them all the information that I know about my tenants (age, names, work, cars, marriage, country of origin, telephone numbers, children) . . . You should expect a visit in the near future."

Grange, 64, forms a fist and frowns.

"Their hands were shaking as I read the letter -- they were scared stiff," said the priest, who is a founding member of South Bronx Churches, an ecumenical organizing group that is helping the women. "Evil has reared its head and threatens to ruin their hardworking lives."

Much has changed in the post-Sept. 11, 2001, world of New York. There are subway announcements advising riders to watch for suspicious people and unattended packages. There is the shared memory of attacks past and the fear of more to come. And for some of the hundreds of thousands of immigrants in the city, especially those whose visa papers are not in order, the fear is doubled. They worry about more attacks and about those who might take advantage of them in these troubled times.

"This case in the Bronx is a particularly flagrant example of what our constituency faces with some frequency," said Andrew Friedman, co-director of Make the Road by Walking, an immigrant advocacy group that has worked with tenants in Brooklyn who have received similar verbal threats from landlords. "People put up with absolutely ghastly living conditions and feel they can't complain in this security-conscious world."

The Asian American Legal Defense and Education Fund handled several cases in the past year in which landlords tried to intimidate Muslim tenants by threatening to call the FBI. An organizer who works with nannies said that such threats are common -- and that they recently won a court case for back wages against a tennis instructor who warned he would call the Department of Homeland Security.

"We hear about this quite often -- it's our main challenge, because employers know everyone is so scared now," said Ai-jen Poo, who works for Domestic Workers United in the Bronx. "Even people with legal green cards are afraid of deportation post-9/11. It's a double whammy because the economy isn't great."

U.S. Immigration and Customs Enforcement officials in New York report often receiving tips from landlords. "It's very common to hear from landlords," said spokesman Michael Gilhooley. "But our inspectors are careful to balance the tips with the fact that New York has so many immigrants. We prioritize based on threats to public safety."

What is different about the case of the Mexicans in the Bronx is that they received a threat in writing. What is also different is that the tenants did not run. They stood up -- and the landlord seems to be standing down.

"We were scared -- on television you hear all the stories on immigrants and terrorists," said Sandra, 32, who asked that her surname not be used. The walls of her apartment are decorated with images of the Virgin Mary and Jesus and the World Trade Center. "But the landlord's the one who acted like a terrorist."

Landlord Scott Kalb, who owns a dozen buildings in the South Bronx, said in an interview that he did not write the letter. It bears his return address and telephone number, and the type font is the same as his previous letters to tenants. In the interview he referred approvingly to the letter's message.

"It's a whole, big scare thing; you're trying to turn me into a dragon landlord," he said. In reference to his tenants, he said: "You are talking about people who don't even speak English, who are illegal immigrants just like the letter says. Tell me this: What do they know?"

Neighborhood Revival

Grange, a powerfully built man with white hair cropped so close to his scalp he appears bald, grew up here in the 1940s and '50s, when Alexander Avenue was known as the Irish Fifth Avenue. Then came waves of bank disinvestment, white flight and arson. Over the past 30 years, Grange watched the death and rebirth of his childhood streets.

"We lost 60 buildings to arson in one month in the 1970s," he said. "Then the Mexicans started coming about 10 years ago, and this place came back to life. Go to the subway stop at 5:30 a.m., and you get knocked over by everyone going to work."

Just to the south in the Mott Haven neighborhood, near the Harlem River, there is another unlikely revival. Developers are renovating abandoned factory buildings for downtown artists in search of affordable lofts. Kalb, a rough-hewn man, works this revival at both ends. He rents lofts to artists and Alexander Avenue rowhouse apartments to Mexicans.

The Mexican tenants pay between $850 and $1,000 a month for one-bedroom apartments.

Kalb's tenements are not the worst. The front doors lock, and there is heat in the winter. But his Mexican tenants said they found holes in the ceilings, mold in the bathrooms, and broken floors and windowsills. When Kalb balked at repairs, the tenants turned to Grange. He, in turn, put them in touch with South Bronx Churches, an organization affiliated with the Industrial Areas Foundation, a nationwide group also active in the District, Virginia and Prince George's County.

The tenants mailed a list of the worst problems to Kalb. "He called up and said: 'I'm not a slumlord; I'll fix this,' " recalled Marielys Divanne, the lead organizer with South Bronx Churches.

Contractors descended on the Alexander Avenue buildings. Then, just as quickly, the work stopped. When the tenants told Kalb that more work remained, he sent his superintendent around to compile a list of the names and ages of those who lived in the apartments. Four weeks ago, Sandra, who has lived in the building for several years, was sleeping on the couch after work when a child came in with a piece of paper.

It was the letter that appeared to be from the landlord informing tenants that he had been in touch with Homeland Security. "What little we could understand, we were very afraid," Sandra said.

Manuela, whose husband works as a dishwasher, nodded. "We were thinking of leaving. This is no way to live."

Post-Sept. 11 Caution

Earlier this month, South Bronx Churches contacted the city's Housing Preservation and Development, which like many city agencies does not help federal agencies track illegal immigrants who lead otherwise law-abiding lives. The agency's chief counsel warned Kalb that he was flirting with harassment. "We are in such a weird time after 9/11," said Carol Abram, a spokeswoman for HPD. "There can be a fine line between someone who thinks they are doing their civic duty and someone who harasses his tenants. But persistent psychological intimidation is harassment."

Kalb said the criticism is unfair. "Why would I want to force them out?" he asked. "They are paying a very high rent."

As for Manuela and Sandra, they feel the cautious optimism that accompanies respect. "We know people who died in the World Trade Center," Manuela says. "We are immigrants trying to build a better life. We just want respect as human beings."

Marielys Divanne, left, of South Bronx Churches works on behalf of tenants such as Sandra and Manuela, right.

Sandra and Manuela, who withheld their surnames, live on this street.