Nearly 20 years ago, 76 people lost their lives during an FBI raid near Waco, Texas. CNN's Drew Griffin looks at those events at 8 ET/PT and 11 ET/PT Sunday night in "Waco: Faith, Fear & Fire."

Waco, Texas (CNN) -- Sheila Martin's children burned alive. God, she says, wanted it that way.

"I don't expect you to understand," she says, leaning her bird-tiny frame against a full shopping cart in the nursery aisle at a Super Walmart. Her pink shirt, flats and purse match the lilies, hydrangeas and clusters of jasmine she's buying.

"Oh, look, they have forget-me-nots!" She caresses the blue petals and, like a child, puts her nose in the plant and inhales.

"These will be perfect for the memorial."

On Tuesday, Martin and a handful of other surviving Branch Davidians will gather at a hotel off a freeway in this dusty Central Texas town to remember the federal siege on their religious compound, an event that has become synonymous with the word Waco.

On that day in 1993, a 51-day standoff between the armed Davidians and agents with the Bureau of Alcohol, Tobacco and Firearms and the Federal Bureau of Investigation ended in a fire and the deaths of at least 76 people. Among them were Martin's husband and four of her children.

In the garden center, Martin nervously picks up her pace, examining each plant, smelling and touching their blooms, kneading the soil.

The memories have sharpened each year, not dulled as she had hoped.

"I just don't like to go back," she says.

For days on end, grenades went flash-bang, she says, hurting her ears like nails shot into her temples. The kids were screaming, running down the hallway outside their bedrooms when the first shots were fired on February 28.

Bullets hit the walls. They went through the walls. One shattered her bedroom window and zinged over her 6-year-old Daniel's head. She looked up. His face was bleeding, cut from flying shards of glass.

Her 4-year-old, Kimi, was crying. The roar of the helicopters over the building sounded to her like war.

She touches her chest. She still feels the vibration in her ribs from that blaring, awful music the FBI pumped on loud speakers, trying to drive them out.

Her calm, over those days, came when she heard his voice, talking to a negotiator, on the loudspeaker.

"Now, do you know what the name Koresh means?" the voice boomed.

"It means death." Who was David Koresh?

"We didn't have a plan for death," Martin says. "I wondered: Did someone change the plan without telling me?"

On March 21, she walked out of the Davidian complex, one of 21 adults and 14 children who took the chance to leave over those weeks.

Three of her seven children were led out. Four kids stayed behind with their dad.

On April 19, in a Salvation Army shelter where female followers were kept, she saw it on the news: A great fire. It was so big.

"I said, 'Oh, please God, save them. Save them.' But my head knew they were gone."

Martin doesn't visit the pauper's field in Waco where they are buried. "I'm not going to roll around on the dirt crying," she says. "We don't do that."

Branch Davidians believe that when people die, they are simply "unconscious," waiting to be resurrected so they can travel to a kingdom cut off to nonbelievers.

Lisa, 13; Sheila,15; Anita,18; Wayne Jr., 20; and Wayne Sr. -- they are just unconscious. They are just waiting.

David Koresh told his followers years before the men in uniforms arrived that a great apocalyptic battle with Babylon was coming and there would be destruction and fire and deaths.

So, Martin says, David was right. "David is the messiah, and he's coming back," she explains, inspecting a bush that's beginning to produce sweet peppers.

"Now we just wait for the kingdom."

True believers

For more than a decade on every Saturday, the Branch Davidian Sabbath, Sheila Martin and Clive Doyle have gotten together to pray and discuss the Bible. They affirm to each other that David Koresh was God in the flesh. Then, they usually go to lunch or run errands.

They aren't stockpiling machine guns, the chief reason the ATF raided the compound. Between them, Doyle and Martin don't even own a rifle.

While they lived communally on the compound, Doyle and Martin now live in modest homes a few streets apart in Waco. He works at a thrift store. She works at a Christian day care center. Their bosses have asked them to leave their religion at home; otherwise, they've been treated kindly at work and by people in Waco who know about their pasts.

The crank calls Doyle used to get have waned the past few years.

When reporters call about doing stories on Koresh "true believers," they don't participate without talking it over with each other.

"We've come to expect that a lot of people are going to make us look nuthouse crazy," Doyle said, his voice changing to a spooky tone, his face dead-pan. "So, we always like it if we just seem a little crazy -- it's an improvement."

Tooling around Waco in Doyle's beat-up Town & Country minivan, the pair make an odd couple. She is from Boston and in her 60s, but looks, dresses and moves like a teenager. Doyle is a dark-humored Australian who wears thick bifocals and declared at 9-years-old to his amused mother, an Adventist, that he was officially a "servant of God."

"I'm 70," he jokes. "I would like to know where this kingdom is already."

Doyle's legs and arms are a quilt of skin grafts, wounds he says he suffered from jumping through a fiery hole in the burning compound to escape.

The scars are ugly, he says, but nothing compared with the year he spent in prison before going to trial, along with other Davidians, on murder, conspiracy and a string of lesser charges.

Along with the Davidians, four people with ATF were killed during the siege.

Doyle was acquitted.

Evidence that the government gathered, including recordings from bugs planted inside the compound before the FBI's final raid, showed Koresh ordered his followers to set the blaze.

So did they? Doyle is asked.

"Let's say the government created circumstances that led to the fire," he replied.

While Martin and Doyle can be cagey, they are always polite and patient despite people constantly challenging their religious beliefs --- or dismissing them as crazy.

"What am I going to do, argue with everyone?" Doyle says. "When people ask why we still believe in David and what he preached, after everything, I think they are asking because they really do want to understand. What gets lost --- what got lost years ago and resulted in the deaths of many people -- is that none of us were looking to convert the masses. If you joined us, then fine, but if you didn't, then go on with your life.

"You don't have to believe as I do."

Doyle sits in his cluttered living room, detective paperbacks, tomes on theology and Laurel & Hardy videos crammed on bookshelves. The only item that has room to breathe is a photograph of his 18-year-old daughter, Shari.

She was one of Koresh's "wives."

In the photo, Shari is flaxen haired, flushed and smiling, hugging the family dog.

That Koresh bedded his daughter makes Doyle shift in his seat, and when he speaks of it, his jaw tightens.

Doyle says his daughter started having sex with Koresh when she was 14. Koresh fathered at least 13 children with sect followers and engaged in sexual acts with underage Davidian girls, according to the Justice Department, numerous affidavits of Davidians and interviews CNN conducted with survivors. Watch a video Koresh recorded of himself with his children inside the compound during the siege.

Davidian Kiri Jewel testified during 1995 congressional hearings on the siege that Koresh slept in a bed with women and children, and she believed that he had impregnated a 14-year-old. Koresh, she said, often talked about how the young girls at the compound pleased him sexually. Jewel described in graphic detail how Koresh sexually assaulted her. She testified that she wasn't afraid of getting pregnant; she was too young, she explained. She'd not even started menstruating yet.

Doyle insists that his daughter Shari, even at a young age, was capable of deciding whether to have sex with Koresh. The teen was also clearheaded, he says, when she chose to remain inside the compound despite having the chance to leave.

"She wanted to be with David and to hear and follow the message," her father says.

There is silence for a moment. Doyle knows that trying to justify Koresh having sex with underage girls incites nothing but outrage from nonbelievers. And, initially, when David began preaching a message that his holy seed must be spread to any girl he preferred, married or in pigtails, Doyle admits he was bothered by it.

"I wondered, I asked, 'Is this God or is this horny old David?' "

But Doyle's concern didn't last long.

"I couldn't argue because he'd show you where it was in the Bible."

Sheila Martin, too, condones Koresh having sex with underage girls. "In the Bible, if a girl is old enough to menstruate, then she can be a wife," she insists.

There are three crucial points to understanding the Branch Davidian brand of religion.

First, God can appear in the flesh as a man. Second, that man doesn't have to be a good person. Third, if you question whether that man is God, then you are questioning God. In other words, the devil is responsible for your doubt.

"Now," Doyle asks, "are you going to give the devil control?"

Mount Carmel's new residents

Last Sunday, Martin, Doyle, and Doyle's roommate, Ron Goins -- also a Branch Davidian but not a Waco survivor -- packed into Doyle's van and sped down a country road toward Mount Carmel, the property where the compound once stood.

Its acreage is lush with wildflowers, and Martin is soon out of the car, traipsing through prairie grass, picking yellow primrose and butterfly weed.

At the entrance now is a gate --- something Koresh and other members of his inner circle darkly joked they should have built before the raid, Doyle says.

The gate is flanked by several mailboxes. At least three Davidians live on the property, including Charlie Pace, an early Branch member who Martin and Doyle say never got along with Koresh. They say church elders asked him to leave the compound.

"Now Charlie is back to claim what he believes is his," said Doyle.

Pace told CNN that he is "enlightened" and that God chose him to look for fresh believers.

Down a dirt road on the property is a chapel that Branch Davidian supporters built in 1999. On this day, the doors stood open and sheet music and tambourines sat on dusty chairs. A large photograph of a bushy-haired Koresh mugging like Jim Morrison hangs near the door.

The chapel reminds Sheila Martin of the first time this messiah, a high-school dropout in blue jeans, persuaded her to follow him.

It was 1986. She and her husband, Wayne, a Harvard-trained lawyer, were going through a tough time. They were both Adventists and living in New York.

They'd met at an Adventist function; he wooed her with his piano playing.

The births of their first five children had gone smoothly, but their faith was being tested with their sixth, Jamie. He had contracted potentially deadly meningitis, an illness that would cripple him for life.

"I prayed all the time, and I told Wayne that because his faith wasn't as strong as mine -- he'd started to drift into the secular world too much -- that our baby was dying," she recalled.

When Jamie wailed in her arms, with a suffering she was incapable of relieving, Martin thought about her first date with her husband. They went to a performance of Handel's Messiah, the retelling of Christ's victory over sin and death.

"My husband, he heard about what was happening in Waco," she said.

The couple spent hours on the phone talking to the Branch Davidians there. They were always eager to listen, especially a guy who'd recently joined the group, David Koresh.

Koresh mailed the parents a videotape of him preaching. "The scriptures just flowed out of his mouth. He had the spirit of God in him," Sheila says.

Wayne Martin, the pianist, liked that Koresh played the guitar. The church was hurting for a leader with a youthful air.

And their son needed all the in-person prayer he could get.

The couple moved to Waco.

Within days, the Martins were sure they'd made the right choice. When Jamie cried during prayer gatherings, and the others flinched, Koresh went right to the baby.

"He would just pick him up and hold him real tight until he got quiet," Sheila recalled.

Koresh told the Martins that their child needed more healing.

Jamie and two of Sheila Martin's other children survived the fire at Waco. Kimi and Daniel spent the time after the siege with relatives while federal authorities questioned their mother.

Now 22 and 24, Kimi and Daniel now live with their mother in Waco. They didn't want to be interviewed.

Martin says they have rejected the Davidian faith and won't go to any religious events with her. This does not upset her, she says, because she knows that God will eventually change their minds.

"I think they'll realize someday everything is under his order, and they'll understand that it's not really a choice."

Jamie Martin spent his life severely handicapped. He died in 1998.

One day

Sheila Martin likes to paraphrase this scripture: "If you are allowed to drink from the cup of woe, of disappointment, remember it's a loving God who is holding the cup to your lips," she says.

With this, she takes a sip through a straw of chocolate milk after lunch.

"People want life to be sweet, but life isn't sweet and easy," she says. "Not here, not now, but it will be in the kingdom."

What will the kingdom look like?

It will be a physical place, Doyle and Martin say, probably in another country, maybe in Israel. Other than that, they don't know.

"One day, we will have a better experience," Martin says. "We're not going to have to see everyone die."

She imagines it will be like what Diana Ross sang about in the Wiz.

Do you know the lyrics, she asks.

Soon as I get home, soon as I get home

In a different place, in a different time

Different people around me

I would like to know of that different world

And how different they find me

"Diana Ross is singing those words and I'm thinking about Mount Carmel and the way the light would reflect off the snow, and how the snow made everything look clean there," Martin says.

"What she's singing about is being alone after a great storm that God created and she can't get out of her circumstance.

"I'm going to keep praying, and wishing for that place, for me and Clive."