THE SOUND OF a dog yapping on Saturday morning led landlord Turgut Gozleveli down into the lower basement of the Northeast Philadelphia apartment building he owned, down to an abandoned boiler room that was bizarrely locked shut with a chain wrapped around the door handle.

Gozleveli, 71, unwrapped the chain and opened the door, smelling urine and the earthiness of the dirt floor mixed into something he could only describe as a "horrible smell, like unexpected, like undesirable smell - the urine smell."

In the dark, with the light from his flashlight, he saw two little dogs, like Chihuahuas, blankets, pillows and makeshift mattresses. He pulled one blanket up and was stunned to see two faces - a man's and a woman's.

"I said, 'What the hell you guys doing there?' " Gozleveli, originally from Turkey, recalled yesterday in a heavily accented voice during a phone interview. "There was no answer. Then I closed the door and called police."

Gozleveli, who doesn't live in the tan stucco apartment building on Longshore Avenue near Vandike Street in Tacony, called 9-1-1 about 10:30 a.m. Saturday. He said that at first he thought the people were in the basement sheltering from the cold and the rain, but that he didn't know how they got there.

After police arrived, he led them back down to the sub-basement, where police found four people being held captive - one chained by his ankle to the old, metal boiler.

All four victims - a woman, 29, and three men, 31, 35 and 41 - were discovered to have mental disabilities, said police spokesman Lt. Ray Evers. The oldest man was the one shackled.

"They had bedsores, were very, very thin," he said. "Physically, they did not look in good condition. They were definitely malnourished."

"The responding officers knew right away" that they were "dealing with special-needs people," Evers said, adding that the captives were locked in what looked like "a dungeon" with a bucket of urine and feces inside.

Gozleveli said it was after police came that he found another dog - a large, quiet one that didn't bark - in the upper basement, above where the captives and two small dogs were found. That room was dark, the lightbulbs missing from the ceiling.

The victims were taken to Aria Health Frankford, where they were treated and then released Saturday night into a city mental-health facility, said Evers.

Police yesterday charged three suspects in connection with an apparent kidnapping and possible human-trafficking case in a suspected scheme to cash in on the victims' Social Security disability checks.

Linda Ann Weston, 51, and her boyfriend, Gregory Thomas, 47, were arrested Saturday night at a rowhouse on 29th Street near Huntingdon in North Philly. Eddie Wright, 50, was arrested in the Longshore Avenue apartment building, said Officer Tanya Little, a police spokeswoman.

Weston, the alleged mastermind of the scheme, was previously convicted of third-degree murder for holding captive 25-year-old Bernardo Ramos, who was the father of her sister's unborn baby. Weston and her sister held Ramos captive in a closet in an apartment they lived at on 33rd Street near Berks in Strawberry Mansion for two months until he died of starvation in 1981. Police later found Ramos' body in an abandoned Spring Garden house.

Police yesterday said Wright was previously from Texas. They said the four victims found Saturday had lived in Texas for some time, then in Florida's West Palm Beach area for about a year and a half before being brought to Philadelphia the week of Oct. 3.

"It's not yet clear whether" the victims were imprisoned in Texas and Florida as well, Little said. But the three suspects and four victims "all drove from Florida together" to Philadelphia, she said. The FBI is also investigating.

Weston, Thomas and Wright were charged with conspiracy, aggravated assault, kidnapping, criminal trespass, unlawful restraint and false imprisonment.

A daughter of Weston's lives in a second-floor apartment of the Longshore Avenue building where the victims were found. Little said the woman is not believed to have known what was going on.

Other residents in the apartment building and neighbors also said they didn't know there was a grisly prison on their block.

Block captain Danyell "Nicky" Tisdale, 41, standing outside the building yesterday as a CNN news vehicle was parked nearby, said that one late night about two weeks ago, she saw an SUV pull up. Weston and Thomas got out of the front and three men, who appeared mentally disabled, climbed out from the back, she said.

Then, two Sundays ago, Tisdale, who lives a few doors down, said she saw the three disabled men being ordered by Weston as they separated clothes on the sidewalk in an effort to sell them as part of a "flea market."

Rhasheda Hamilton, 34, who lives in the building, said she didn't hear anything from her second-floor apartment.

"The crazy thing was it was rumored that people were living in the basement, just sleeping," she said.

Ana White, 24, who lives in a first-floor apartment in the building and works with mentally challenged people, said she didn't even know there was a sub-basement and had just heard that new people moved in recently.

A neighbor who lives a few doors down and identified himself as Ed said he came home two Sundays ago from fishing. He caught about 20 bluefish, about two feet in length, from the Atlantic off Brielle, Monmouth County. Since he had so many, he gave some away to neighbors.

He even gave some to a man with a silver minivan who said he "just came up from Florida," Ed, 56, recalled. When later shown by the Daily News the mug shots of the two male suspects, Ed said the man he spoke with was Thomas.

Thomas was grateful for the fish. "Oh, thanks, this will feed a lot of people that are hungry right now," Ed recalled Thomas saying.

Thomas and Weston, who were arrested in Thomas' cousin's house, didn't live there, the cousin, Rob Taylor, 66, said yesterday.

Taylor said he came home Saturday night to find Thomas and Weston inside; they had been let in by his wife. Then, cops came to the door. Taylor opened it, and they arrested Thomas and Weston.

Taylor had no idea about anything the two might have done. But after he heard the news, he blamed Weston.

"Greg, he don't have that kind of education to do that," he said of the alleged Social Security benefits scheme. "She [Weston] says what goes on, that's just how it is."