The ultrasound wand skimmed across Melissa Buckles' belly. Eighteen weeks along, and she was already joking that she felt like an Oompa Loompa. Now she and her husband, Kevin, watched the blurry image take form on the monitor. Look, the technician said, there's one head, and there's another. Twin girls! Melissa and Kevin burst out laughing. They would later remember just 20 sweet seconds of anticipation.

Then the ultrasound wand paused and the technician fell silent.

Are you Christian? she suddenly asked.

The Buckleses were perplexed. Yes, they said. But what did faith have to do with this?

This is going to be a difficult pregnancy, the technician went on. They're conjoined.

"I was shocked and terrified," Melissa recalled later. "I thought: Isn't that something that only happens in Third World countries?

"How can this be?"

A doctor came into the exam room and studied the monitor. The girls, he said, were connected from navel to breastbone, facing each other. The hearts and stomachs were separate, a good sign. The girls appeared to share a liver, and their diaphragms were distinct but fused.

Conjoined twins are the rarest of human births; barely 700 sets have been born alive in recorded history. But if the Buckles twins managed to make it to term, there was a chance they might be successfully separated, and go on to enjoy normal lives.

Against those staggering odds, Jade Hope and Erin Faith Buckles were pulled from the womb on Feb. 26, six weeks premature. Together they weighed nearly 10 pounds and proved so robust despite their deformity that they were sent home after just a week in the intensive care unit.

Since then, their parents, their doctors and the babies themselves have struggled down a largely unmarked road to separation. For the past four months, it has been a journey that has challenged and frightened the Buckleses, empowered them and humbled them.

Every procedure, every test, every plan, every prayer comes down to this:

Tomorrow, surgeons at Children's Hospital in the District will try to divide one small body into two.

Taking the Chance

No one knew what to say.

Even the grandmothers met the news with stunned, teary silence. Close friends apologized. Melissa broke down weeping in front of her high school English students.

Kevin, a 34-year-old Marine gunnery sergeant, and Melissa, 30, wanted another child but hadn't planned on it this soon. Melissa had just started teaching again and was loving her new job at Forest Park High School. They were fixing up their new Woodbridge townhouse and getting their 2-year-old daughter, Taylor Joy, settled into day care. Kevin shared custody of his 11-year-old son, Kevin Jr., and the third bedroom went to him. Suddenly, what had seemed like a spacious house was going to be crowded.

Still, the pregnancy was a happy surprise. Terminating it wasn't an option, they both said, even after learning that the twins were conjoined.

As long as there was a chance, they would take it.

The Buckleses confided in just a handful of friends and family members. Everyone else was told only that it was a complicated pregnancy. Melissa was confined to bed rest.

"We didn't buy any baby furniture, any baby clothes, any baby anything," recalled Kevin, an assistant drum major in the Marine Drum and Bugle Corps.

"It would have been too much of an emotional investment," added Melissa.

Their case was transferred to National Naval Medical Center in Bethesda, the nearest military facility equipped to handle such high-risk deliveries, to the ward where Christian Macedonia routinely greets his patients on morning rounds with the same plea: "Please be boring today." The Buckleses promised to be anything but. Macedonia and the delivery team began rehearsing long before delivery; how would they turn the babies if they were breach, how could they intubate? "It's kind of a push me-pull you situation," Macedonia realized.

Melissa was hospitalized shortly before Christmas so doctors could monitor her more closely. For the next three months, she played games on her laptop computer, watched countless DVDs and sang quietly to the babies kicking like synchronized swimmers inside her. After one of her students came by and taught her to crochet, she started a baby blanket she couldn't bring herself to finish. Time she had in abundance. Faith was harder to come by.

As the pregnancy progressed, sophisticated ultrasound images showed the girls in vivid detail; Kevin and Melissa could see not only fingers and toes, but individual hairs on their daughters' heads. The couple grew accustomed to the sight of the fleshy bridge where the girls' torsos fused into one. Sometimes one sister looked as though she were whispering in the other's ear. Tiny dance partners, Macedonia called them. Melissa began having contractions in her 34th week; already the babies' heart rates were slowing, a common side effect of prolonged bed rest.

"We're delivering tomorrow," Macedonia announced.

Splayed on the operating table the next morning, being prepped for her Caesarean, Melissa suddenly felt faint. She could hear nurses trying to find heart rates on the fetal monitors. She felt them scanning her belly; the epidural hadn't taken yet.

"Suddenly I heard someone say: 'We have to go now! It's a crash!' The anesthesiologist was trying to tell them I wasn't completely numb but they had to make the incision," she recalled.

Kevin was in the hall making a phone call, waiting to be summoned for the delivery, unaware of the drama unfolding behind the OR door.

Melissa felt the surgeon's knife slice the length of her stomach. She dug her fingernails into the palms of her hand, leaving imprints that would take a week to fade. The pain was excruciating.

"At 10:30, they cut me. I heard the doctor saying, 'I got feet.' The babies were out at 10:31."

Kevin barreled into the room, angry and scared. "Go check the babies, go check the babies," Melissa begged.

Jade and Erin were alive and well, breathing on their own.

The Challenges of Care

Soon enough, they were home. The parents fell into a sleepless routine of caring for the twins. They mastered the art of crisscross feeding, using doll-sized bottles because nothing bigger could fit between two faces locked mere inches apart. Slipping diapers on sideways, with four tiny legs kicking, became an acrobatic stunt performed two dozen times a day. Because the babies could lie only on their sides, bedsores were a worry; they had to be turned over every hour or two.

Kevin tried to reconfigure a baby swing to hold them, just to offer a change of position and scenery. The car seat was a tougher riddle: It took biomedical engineers at the National Institutes of Health to jury-rig a padded carrier that could hold both girls, but Melissa still had to ride next to them. If either Jade or Erin fell asleep and her head lolled forward, she could easily smother her twin. They outgrew the car seat in a week. Outings were limited to medical appointments anyway, so the girls wouldn't be exposed to gawking strangers or life-threatening germs.

As difficult as it was to care for the girls, Kevin, a self-described "total control freak," found it harder still to admit that the family needed a hand.

"I had to swallow hard," he said. "Just as a man, and a Marine. To have to ask for help . . . that's not our role." But they'd lost Melissa's income months before anticipated, and Kevin's military paycheck wasn't going to cover the mortgage, car repairs, everyday expenses plus the special needs of the twins. They had no idea whether insurance would cover all medical expenses; even 10 percent of those costs would bankrupt them.

A military support group wrote Kevin a blank check to stock up at Babies "R" Us. Another Bethesda patient who had just lost a baby gave the Buckleses her new crib. Children's Hospital persuaded a car dealership -- Manhattan Auto in Rockville -- to donate a van, and Chevy Chase Bank seeded a trust fund with $10,000. The hospital's biomedical engineer built a bigger car bed for the twins, then drove 21/2 hours through torrential rain one night to deliver it to the Buckleses' home. Back in Melissa's native Minnesota, her family's church sent quilts, and her mother got out her sewing machine, puzzling over how to stitch baby clothes to fit her new granddaughters.

At Children's Hospital, a task force of two dozen specialists began mapping out the extraordinary operation to separate the girls. Leading the team would be Gary Hartman, a pediatric surgeon with three such surgeries already to his credit. At weekly roundtables, the specialists strategized. Hearts and skin, they quickly determined, would pose the biggest challenges.

The girls would need twice as much skin to cover the massive surgical wound each child would have. Temporary implants, gradually filled like small water balloons beneath the surface, could force the bridge between the girls to stretch and new tissue to grow.

The twins' hearts appeared to be separate but doctors feared they could share an artery or unseen muscle. That would complicate separation or even preclude it altogether.

Splitting the liver wasn't a problem, since it is the only human organ capable of regenerating. But what if surgeons divided the liver only to discover they couldn't separate the hearts?

Hartman voiced the unthinkable.

"We may have to reconnect them," he cautioned.

They needed to envision even the most remote of possibilities, and that included bringing the girls out of the operating room still conjoined. It was a scenario no one had yet dared paint for the parents.

Diagnostic tests indicated the hearts were in fact separate, but there was still a complication: Sixty percent of Erin's heart protruded into Jade's chest.

"Clearly, it's not going to prevent a successful separation," cardiologist Michael Slack assured the parents.

Melissa began to cry.

"It's such a relief to hear," she said.

The doctor rubbed Kevin's shoulder.

"You gonna smile?" he prodded.

Through bloodshot eyes, Kevin surfaced through his exhaustion and focused. His wife's tears clearly surprised him.

"Did you think it was going to be any other way?" he asked.

'I Want to Be There'

Kevin is a lifelong drummer whose playing days are over. "Carpal tunnel," he shrugged. Now, paperwork replaces music as he tends to the myriad bureaucratic details behind his unit's performances. His commanding officers have urged him to take whatever time he needs now. "Good to see you in uniform, Gunny," Kevin heard a colonel bark when the gunnery sergeant checked in for a few hours recently. "Now go home!"

His method of coping is to stockpile information, to steel himself mercilessly. He has asked, more than once, to be allowed to watch the surgery. Rebuffed, he inquired about a live-feed video into the waiting room. He could handle it, he assured aghast hospital officials, who again refused. The surgeons didn't need the added stress of a parent watching.

Melissa couldn't understand her husband's desire to watch what she couldn't even bear to imagine. "Why?" she finally demanded one day at their kitchen table. Kevin's bravado instantly vanished. His brown eyes betrayed anguish.

"I missed when they were born. I was supposed to be in there and wasn't," he said. "So if something happens, I want to be there. It's not like I'm going to be running in trying to do anything. I just want to be there at that time with the girls."

Their marriage is stronger for this, they believe. They have found both hidden strengths and tender vulnerabilities. "I'm a realist -- like, over the top," Kevin admitted. "I look at death and life differently than she does, knowing that's not the end of the story if both don't make it out of the operating room. It's the cycle. There is a purpose to everything, and the key is understanding it.

"When we found out about the girls, I wasn't surprised necessarily because to me it was just another opportunity to understand more about the Creator and how He works . . . . Someone's got them this far, and it wasn't me, it wasn't Dr. Macedonia, it's not Dr. Hartman."

The twins are 31/2 months old now, with dark, almond eyes and distinct personalities. Jade is the mellow one, able to sleep peacefully even when Erin, the feistier twin, is squalling in her face. They steal pacifiers from each other. They smile at the sound of their mother's voice, wriggling arms and legs with excitement when she leans over their bassinet.

"Part of me wants the surgery to be here," Melissa said. "The other [part of me] doesn't because we have two healthy little girls now. But they would have no quality of life."

She finds herself talking to them constantly, a refrain she knows they can't possibly understand. Her voice is full of hope.

"You need to be brave," she tells them. "You have to be strong. I still need you."

Before she became a mother, Melissa was something of a daredevil. She climbed rocks, rode a motorcycle, swam competitively even after injuring her shoulder three times. But now she has felt shattered, unsure. Even the finale of "Friends" made her weepy.

"I think it will be pretty traumatic for them to be separated," she said. "They comfort each other now, touch each other's face or hold hands. Initially when they reach out and suddenly can't feel their sister, there will have to be some shock."

The hospital staff has coached the Buckleses on ways to ease any emotional impact that separation could have on the twins. Before tomorrow's surgery, the parents were planning to record Jade and Erin gurgling and cooing to one another; when the girls are in separate isolettes across the ICU from one another, nurses can play the tapes to soothe them. Pieces of soft cloth bearing the other twin's scent can be held under the girls' noses as they recover, and the hospital staff was considering placing mini-sandbags next to the girls' bodies to simulate the comforting weight of a sister suddenly gone.

For all the careful planning, though, the unexpected can still whipsaw the whole parade out of formation.

Last week, Melissa's mother arrived to help out, then fell down the stairs and fractured an ankle. The downstairs toilet broke. The bill for one day of tests for the twins and a single night in the hospital came in the mail: $59,428.65.

Then the separation itself was postponed for a week to allow for more skin growth.

And this week, when the tissue expanders were filled with more saline solution, Jade's eyes began moving rapidly back and forth. It happened twice again at home that night. Doctors worried that she might have suffered a stroke or seizure, which could delay the surgery indefinitely.

"Back on the road again," Kevin told the twins Tuesday before scooping them up for the trip to Children's for Jade's brain scan. "You all are road dogs."

Melissa got up slowly from the sofa. "I have a monster headache," she said.

The Medical Dance

Jade's tests come back normal. The 28 boxes on the task force's "Go, No Go" checklist are all marked "yes."

Kevin has his own sheaf of papers. He has drawn up a schedule for the hours he and Melissa will spend together and separately in the ICU as the babies recover. Let us take over, the nurses have admonished him. When your children go home, they will need parents who aren't frazzled and exhausted.

Kevin sat in on one of the task force's last meetings, while Melissa stayed home with the girls. The doctors laid it all out for him, walked him step-by-step through the medical ballet they had so elaborately choreographed. He drank in the information and then spoke up. He acknowledged that there were geniuses in the room, that the technology available was mind-blowing, the machines at their disposal extraordinary. He thanked them for all their planning.

"But when all is said and done," he concluded, "it's not in your hands whether they live or die."

Days later, he went to his barracks and pulled his closest friend, a horn player, into the hallway.

The surgery was soon, he reminded his buddy. "If things don't go right, and one or both girls die, I want you to play taps for them."

Children's has been documenting every aspect of Jade and Erin's care, and video cameras will record the operation. Their case will be outlined in medical journals and discussed in classrooms. But there is a part, their father knows, that never can be analyzed clinically.

"We can't control when we're born, and we can't control when we die," Kevin said, sweeping the girls into his arms for another trip to the hospital. "And it's just vanity to think we can control anything in between."

Melissa Buckles holds her 4-month-old conjoined twins Jade and Erin as daughter Taylor, 2, comforts them after an appointment at Children's Hospital in the District. After months of planning and prayers, the twins are scheduled to be separated tomorrow at the hospital. Kevin and Melissa Buckles and their children Taylor, 2, and Kevin Jr., 11, visit Jade and Erin in the recovery area after a procedure at Children's Hospital to implant expanders to stretch the twins' skin.Melissa Buckles speaks with Master Sgt. Mark Miller, right. Left, her daughter Taylor is held by Gunnery Sgt. Reginald G. Jackson. Melissa Buckles holds her twins at their home in Woodbridge the night before a medical procedure. Daughter Taylor, 2, does somersaults.Kevin Buckles, resting his head as he bathes Taylor in their Woodbridge home, says he has had trouble asking for help since the twins were born."Part of me wants the surgery to be here," says Melissa Buckles, with Jade and Erin.