Eighteen days after infant Sabrina Aisenberg disappeared--even as neighbors held candlelight prayer vigils and her mother went on television to plead for her safe return--suspicious investigators secretly sought a judge's permission to eavesdrop on her parents, court records show.

Even before the appeals of Steven B. and Marlene J. Aisenberg grew from a local plea for help into a national crusade that played on prime-time television, detectives from the Hillsborough County sheriff's office had slipped into the four-bedroom stucco house on Springville Drive to plant an electronic bug.

They listened in for three months, ending in March 1998, records show. But the first indication of what authorities say they heard became public only this week after FBI agents battered through the front door of the Montgomery County house where they had lived since May.

The indictment filed in U.S. District Court in Greenbelt on Thursday charges them with conspiracy and with lying to investigators--but not with killing Sabrina. It quotes Marlene, 36, as saying the baby was "dead and buried" and Steven, 35, stressing the need to "beat the charge."

In one moment of remorse, according to prosecutor Rachelle Des Vaux Bedke, Steven said: "I wish I hadn't harmed her. It was the cocaine." At another point, Marlene apparently became upset that frames from a family video--made two days before Sabrina disappeared--had been blown up by police to show bruises on the child's face. The indictment said she told her husband they would need a lawyer to help them explain the injuries.

Though prosecutors say they believe the child is dead, her body has not been found. The couple's attorneys say authorities lack the evidence to bring murder charges, so they hope to pressure one parent into implicating the other. The Aisenbergs each posted $25,000 bail in Maryland and are expected to return to Florida to be arraigned.

The quiet cul-de-sac east of Tampa in a subdivision called Bloomingdale drew the curious today, with cars creeping along the narrow street lined with stately brick homes and bright stucco houses graced with crape myrtles and mailbox flower planters. They slowed in front of the house at 3632 Springville Dr., which the Aisenbergs bought for $117,600 in 1993 and have had on the market since moving into his boyhood home in Montgomery.

"Another sightseer, I guess," said Martha Jones, who lives next door to the Aisenberg house, as a couple in a passing car peered first at the house and then at her. "It was nice, because the neighborhood got back to normal in the past year, and now this . . . "

Today, "I think we all feel used and lied to," she said.

Marlene Aisenberg showed up on Jones's doorstep with another neighbor Nov. 24, 1997, 10 minutes after reporting 5-month-old Sabrina missing.

"Her demeanor was just not consistent with what you'd expect," Jones said. "She was weird, unemotional and detached."

That was in sharp contrast, Jones said, to Aisenberg's behavior about a year earlier when she knocked on her door in a frantic search for her other daughter, Monica, who had wandered off.

"She was hysterical," Jones said. Monica was found a few minutes later, but the memory nags at Jones because Aisenberg's reaction to Sabrina's disappearance was so sedate in comparison.

Still, she initially accepted the couple's report that someone had abducted the child, and she joined in the massive effort to find the infant.

"I called up radio stations to defend her, to say that she did often leave the garage door open and it was possible that someone could have gotten in," Jones said.

Not long after that, however, the Aisenbergs took their attorney's advice to make television appeals for their daughter's return. Jones said she began to feel that everything they said didn't add up.

For example, they said that the child disappeared between midnight and dawn on a night when they had left the garage door open and the front door unlocked, and that their dog, a mixed breed named Brownie, didn't alert them to an intruder.

"They said their dog wasn't a barker. She was a barker," Jones said today. "We'd pull up in the driveway, and she'd bark."

Jones discounts the contention of the Aisenbergs' attorneys, who say the conversations authorities say they overheard are being quoted out of context. She described Steven Aisenberg as "the yeller" of the family.

"People don't talk about dead babies," she said. "If there isn't something to it, if it isn't true, it wouldn't be on the tape."

"If she's not guilty of murder, she should come forward and say what needs to be said," Jones said of Marlene Aisenberg. "Tell the truth."

The neighbor who first heard from Marlene Aisenberg on the morning of the baby's disappearance, and who accompanied Marlene to Martha Jones's house, has moved away from Springville Drive and asked not to be identified.

The woman, who works in a local grocery store that donated Thanksgiving dinner to the Aisenbergs in the days after Sabrina's disappearance, said the indictment has left her with a sense of betrayal, because she and so many others in the community rallied to support the family.

"I'm really glad that it's coming to an end, but I'm just really sad for the baby," she said.

In a town that residents describe as close-knit, several people said they were not shocked at news of the indictment.

"It wasn't a surprise," said Kevin Mulholland, manager of an Albertsons grocery store near the Bloomingdale subdivision. "Not after all this time."