He opened the door, and a hot, stifling stench came crashing through the corridor.

And that sickly smell—or more aptly, the anonymous complaints about it—is what brought an animal-hoarding interventionist here in the first place. Allison Cardona, the chief hoarding investigator at the Manhattan-based ASPCA, has conducted these types of rescue missions all over New York City lately. In 2005 the ASPCA, as part of the Mayor's Alliance for NYC's Animals, helped the city get thousands of dollars in grant money to launch an anti-hoarding program. Administered by the city's Department of Health, the pilot project pairs Cardona with a social worker who hooks up troubled hoarders with medical care, food stamps, and other services. Cardona, meanwhile, deals with the animals—first, spaying and neutering them; and then, trying to place them in adopted homes.

Over the past 18 months, the program has seen 80 hoarding cases in total, spanning all five boroughs and every ethnic group and income level. Most of those cases (59) involved women. But gender aside, the average animal hoarder fits a pretty typical profile: They tend to be elderly, isolated, and lacking in resources. They are, in short, people like Steven.

"I haven't had anybody in this apartment since maybe 2002," he said as he entered his one-bedroom apartment. His wife, Hazel, had to leave their home for a nursing facility in Riverdale three years earlier. These days Steven survives on a $200 monthly allowance from his estranged sister and lives with his cats, all 35 of them, each one now scrambling, screeching, and scurrying around the apartment.

From the looks of it, Steven's cats had taken over his abode a long time ago. Gone were the cushions on his red sofa, for instance, which was shredded down to its bare wooden frame in multiple places. Ditto for the vinyl blinds, and the padding on the kitchen chairs. Large claw marks dotted every wall; tiny scratch marks decorated every piece of furniture—from tables to bookshelves to kitchen appliances. Dust, inches thick and intertwined with cat hair, blanketed the environment. Flies buzzed and swarmed around the rooms; maggots contaminated the litter boxes.

Cardona, who wore an orange T-shirt with the words ASPCA: We Are Their Voice, walked around the unit, inspecting it with a careful gaze, scrawling notes in a folder. She had heard about Steven from an ASPCA law-enforcement officer who had fielded the anonymous complaints about the foul odor. But when the officer decided that Steven wasn't abusing his cats (and could therefore not, legally, seize them), he referred the case to Cardona, whose job it is to persuade Steven to lower his animal load voluntarily.

During this particular visit, she was taking an inventory of the orange and black tiger and tabby cats, the ones perched on top of the refrigerator and nestled in the sink and camped inside the sofa. Four tiny kittens frolicked about in an empty Pyrex pan on the floor.

"Is that the nursing cat?" Cardona asked, as Steven reached for one of the rattier animals. He nodded, the grayish tiger cat wiggling violently in his arms.

"I think she might need more food," Cardona said, feeling the cat's frame. "She's too thin to be a nursing cat."

"Oh, no. She's OK," he replied, explaining that he feeds his cats two times a day, which eats up $75 of that monthly allowance.

"I'm telling you that she's not," Cardona responded, firmly.

"Yes, she is. She's healthy. She'll be all right," he persisted.

Like most hoarders, Steven didn't start out that way. In 2000, he stumbled upon three stray kittens outside his building. One year later, he brought in another cat, hit by a car, stranded on the front stoop.

"They all started multiplying," he explained. Four cats reproduced three times over the ensuing six years, leaving him with nearly three dozen.

Steven thinks of himself as simply a man who loves his animals. "I consider them my companions," he told Cardona, as a half-dozen or so cats moved in around his feet. "They're smarter than a lot of people, and they never, ever disappoint," he said. Besides, now that his wife has left, they've given him a reason to get up in the morning. "I would have cracked up if I didn't have something to get me going. They forced me to clean up their mess."

Still, he confided, it's a lot of work. In recent months, his cats have knocked over candles, turned on the gas stove, and gotten into the cabinets. One day last summer, they turned on the faucet and flooded his entire apartment.

"I'm going insane," he told Cardona. "This whole place is not amenable to a good life."

Cardona made an appointment to return in a week to have all the cats spayed and neutered; the next step would be adoption. As he walked her out of the apartment, Steven agreed to give up his companions, but said he'd like to hold on to three of them.

It's a lucky number, he said.