The full version of "Operation Hope" is now available on this page. Part One tops this piece; click on the thumbnail pics on the left side of this story to watch Parts Two and Three.

(CNN) -- "You cannot die! You cannot die!" the father mumbles to the bloodied, mutilated boy who lies unconscious on his lap.

His hands press down on the boy's slashed-open stomach to keep the insides from spilling out. He sobs convulsively.

"Listen to me! You cannot die!" he repeats his morbid mantra. "If for nothing else, to exact justice."

Click here to find out how you can help

The two are on a rickshaw headed to a hospital in Dhaka. It's not the most effective way to transport a dying child through the cramped, congested streets of the Bangladeshi capital. But it's all that the impoverished father can afford.

Hours earlier, four men had surrounded the 7-year-old boy, bound his hands and feet and cracked open his head with a brick. They held him down and took a switchblade to his throat. They sliced his chest and belly in an upside down cross.

Read: A terrible lesson, how Sara Sidner found the story

And in a final brutal act, they hacked him sideways, chopping off his penis and his right testicle.

"It's amazing that he lived," a doctor would later say. "I'm really surprised he didn't bleed to death prior to getting to the hospital."

This is the story of a boy who not only survived, but is now the key witness in a trial that has forced Bangladesh to confront the cruel but overlooked practice of forced begging.

It is also the story of strangers, half a world away, who set out to show the boy that good exists in equal measure as evil -- and who set off a chain reaction of kindness to make him whole again.

For his safety, CNN has chosen to withhold the boy's real name.

For his resiliency, we will call him "Okkhoy" -- the Bengali word for "unbreakable."

'Pure evil'

It is now almost two years later. Deep scars still crisscross Okkhoy's frail body.

He is afraid to go out after dark. When sleep finally comes, he wakes up screaming. "Hush, hush," his father -- whom we are calling "Abed" -- reassures him. "As long as I'm here, the devil cannot get to you again."

The attack took place in late 2010, just a few days before the Muslim festival of Eid. Three area kids lured Okkhoy out of his home with the promise of a popsicle.

"They kept insisting that I go down to this one area," Okkhoy recounts. "I kept saying, 'Why?'"

His suspicions aroused, Okkhoy says he set off for home when a group of neighborhood men grabbed him and pulled him into an alley.

"They tied me up and told me they'd force me to beg," he says. "I told them, 'I know each and every one of you. And I'm going to tell my father.'"

That's when one of the men grabbed a brick and struck him across the head, he says.

He fell to the ground and, mercifully, lost consciousness. Because what followed was even worse -- an act that authorities dubbed "pure evil."

"This little child who has his whole future ahead of him, they all but killed him," says Mohammed Sohail, a commander with Bangladesh's elite anti-crime unit, the Rapid Action Battalion. "They thought he was gone. Dead."

The attackers left Okkhoy by the side of a warehouse, intending to come back later and dump him in the river.

His mother, who had gone looking for her missing child, found him.

"I barely recognized him; he was so stained with blood," she remembers.

With every ounce of energy she could muster, the hysterical mother carried Okkhoy's limp body to the side of the main road. "Who killed my baby? Who killed my baby?" she wailed.

Abed, alerted by a neighbor, rushed to the scene -- and the gory sight.

"It felt like the sky fell on me," he says. "As a father, there is no greater pain in the world than knowing that you could not protect your child."

Okkhoy spent three months in a Dhaka hospital, where doctors stitched up his wounds. But they were unable to do much to repair the severed organ.

A despicable practice

For most Westerners, the issue of forced begging was thrust into the spotlight in the 2008 Oscar-winning movie "Slumdog Millionaire," in which a child in Mumbai, India, is intentionally blinded so he could bring in more money in alms.

But the existence and prevalence of "beggar mafias" is an open secret in South Asian countries.

Pity pays.

So, the gangs kidnap and cripple children -- knowing sympathetic passersby are more likely to be touched by, and give to, a limbless child.

Almost half of Bangladesh's 150 million people live on less than a dollar a day. The economy has slowed; poverty is skyrocketing.

And each new day brings a fresh batch of sun-caked boys and girls who tap on car windows to draw attention to their disfigurement -- a desperate way to survive.

The U.S. State Department, in its 2012 Trafficking in Persons report, cited forced begging as one of the areas where Bangladesh needs to develop a comprehensive approach of prevention and prosecution.

Begging is banned in the country -- at least in its penal code. And a three-year prison term awaits anyone caught forcing someone to beg.

But enforcement is lax and for now, the ring masters in this cruel circus remain above the law.

A nation outraged

Okkhoy's case would have gone unnoticed were it not for his father's chance meeting with a human rights lawyer, Alena Khan.

When Abed went to the police to report the attack, he was told a case was already in the books.

Someone who identified himself as the boy's uncle had told police that Okkhoy was assaulted by two boys in a playground spat that turned ugly.

Read and watch Sara Sidner's report on the attack from May 2011

"Two little boys are capable of such brutality? And you believe that?" the incredulous father asked.

"Yes, now let us do our job," he was told and dismissed.

Undeterred, Abed decided to appeal to a judge. But there, too, he was told to let the police handle the matter.

In the courthouse that day was Khan who, as founder of Bangladesh Human Rights Foundation, has made a career of upsetting the status quo.

When a university student was tortured to death in police custody, she represented the family. When officers raped a woman and destroyed evidence, she dragged them to court. And when a high-ranking police official sold orphaned children from his home, she secured his conviction.

"I saw the father standing there helplessly before the judge, and I kept thinking that there's a child who has been broken beyond repair," she recalls.

Khan decided the first thing the case needed was attention, and she contacted a local television station.

"No child should go through this," she says.

The response from an outraged nation was immediate.

The high court asked authorities to launch an inquiry.

And within days, the Rapid Action Battalion rounded up five suspects and charged them with attempted murder.

"The boy started arguing with us and I hit him on his head with a brick," said one of the men in a televised confession.

In a chilling monotone, he recounted the assault, naming each of the attackers.

"After I hit him on the head, he fell to the ground. Then (one of the men) said to cut off his penis, and I cut it off. After that, (someone else) cut his chest and belly. Then (a third person) held his head and slit his throat."

Why did they target Okkhoy?

It was payback, his father says.

Abed had gotten into an argument with one of the men at a tea stall.

"He said to me, 'Just you wait and see. I will take your son and make him work for me.'"

Authorities continue to look for four others who they say are part of the same gang. To ensure Okkhoy and his family stay safe, they were placed in a battalion compound.

"As long as it has its venom, a snake will always attack," Abed says. "Who knows how many other children this gang did this to? Because we're the family that unmasked them, they will always want to destroy us."

A simple e-mail

Among the networks that aired Okkhoy's story was CNN. And among those watching it was a businessman some 8,000 miles away in Columbus, Ohio, named Aram Kovach.

"Usually we see something horrible on TV and we go, 'Oh goodness, that's horrible.' But then we move on,'' Kovach says.

But this story, he says, "kept getting progressively worse and worse and worse."

"You got to the end, and I was like, 'All right, this is unbelievable. We have got to help this kid. We have got to do something.'"

By his own admission, Kovach has had a comfortable life.

His father was a nuclear physicist in Yugoslavia, so sought after that the U.S. government handed the family its immigration documents in an envelope while they were vacationing by the Adriatic Sea, and whisked them by plane to the States.

"I was 12 then and I wrote to my friends, 'You have to come to America,'" he remembers. "We came like royalty, like rock stars. I had no idea that's not the experience of most people."

Today, Kovach's company creates technology for clients trying to spruce up their e-commerce presence -- and he makes a decent living doing so.

He has always wanted to get involved in philanthropy but always thought he needed to be further along in his career.

"I read about the Warren Buffetts and the Bill Gates who have millions and millions of dollars, and I always felt like when I get to that point -- when I have so much money I don't know what to do with myself -- that's when I am going to act."

A few days later, Kovach fired off a simple e-mail to CNN.

"I was so moved by this story that for several days now I can't seem to get it out of my head," it said. "My wife and I would like to somehow help his family and their little boy."

Five minutes of television was about to change the lives of two families.

Unanswered questions

Urologists in Bangladesh had done their best to preserve the boy's urethra, the tube through which we urinate. They bore a tiny hole so Okkhoy could stand up and relieve himself.

But what he needed was a penis.

The surgery is a specialized one, unavailable in Bangladesh.

"He needs to look like a boy again," Khan says. "The psychological healing can only come after the physical healing."

But there were so many unanswered questions: Will the government let the boy out of protective custody to fly for such a surgery? Where would he go? Who would line up the surgeons? And even if it all worked out, how much would it cost?

There were times when Kovach's wife, Branka, worried whether they were in over their heads.

"I started doing the numbers. 'Maybe we can get 150 people to give $100 dollars each,' we think. Then we think, 'Well, not everybody is going to give $100. Let's see if they give $50.' And all of a sudden, you need to ask 300 people. And it's like, I don't even know if I know 300 people."

But they had their minds made up.

"I have kind of an innate naivete about me where I believe anything is possible," Kovach says.

Months passed.

A worried father

Inside the Rapid Action Battalion compound where Okkhoy and his family lives, the little boy passes his days kicking around a tattered soccer ball. He rides about in a rickety hand-me-down bicycle. At morning call, he stands at attention beside the soldiers.

"He visits me from time to time. I also visit him to time to time and we play together and discuss many things," Sohail, the battalion commander says. "Even after such a thing happened in his life, the boy is still laughing."

But the family, Okkhoy's father says, is irrevocably torn.

Before the attack, they lived in a one-room, tin-roofed shack down a tight littered alley in Kamrangirchar, a landfill-turned-slum in Dhaka that crams more than 400,000 residents in 3 square kilometers (1.15 square miles).

"But back then, life was good," Abed says. "Even if we ate one meal a day, life was good. Now there is this fear in my heart. Yes, we're in protective custody, Yes, they're keeping us safe. But the fear is always there."

The battalion compound is spacious, greener, cleaner.

Okkhoy, his father and older brother live in the men's quarters; his mother and younger sister in the women's.

Abed says his wife spends her days in a daze, mumbling incoherently to herself. "Allah, give back to my son what they took away," she prays daily.

He, too, confesses to breaking down when his son isn't around.

"They destroyed our lives, They destroyed our family. There is no hope for us anymore," he says.

Okkhoy has never been to school. He has a single-minded goal: He wants to join the battalion -- and see his attackers hanged.

"I want to be a RAB member and nothing else," he says. "When I grow up, I want to bring them to justice."

Such talk worries his father.

"My biggest fear is that he'll start to think, 'I will find the person who did this to me and I will do the same to him.' He will live in a world of revenge.

"I don't want this. I don't want to be the father of a terrorist."

The pieces fit

John Gearhart is the director of pediatric urology at Johns Hopkins Children's Center in Baltimore, Maryland.

As one of the nation's preeminent urologists, he has treated hundreds of children born with birth defects or ambiguous genitalia.

If anyone could make Okkhoy whole again, he could.

So, CNN reaches out to him. And he agrees.

"You just can't imagine another human being doing this to another human being, frankly," he says. "And even though he is Bangladesh and I'm in Baltimore, to be able to change one child's life is why you go into pediatrics."

Gearhart then enlists the help of a few other colleagues, who -- like him -- volunteer to donate their time.

With a medical team ready, the rest of the pieces quickly fall into place.

Qatar Airways offers to fly in Okkhoy for free. Staffers at the Bangladesh office of International Organization for Migration prepare him for what to expect in the United States. And Kovach agrees to bear the rest of the family's expenses.

"They say angels live in heaven," an ecstatic Abed exclaims. "These compassionate souls are proof they live among us too."

A nagging question

It's late afternoon when father and son, accompanied by their court-appointed guardian Alena Khan, fly into Dulles International Airport. It'll take another hour in rush-hour Friday traffic to arrive at the townhouse near the Baltimore hospital where the family will live for the next month.

"You've been on our minds for about a year or so. So, I'm glad to meet you and I'm glad that you are here," Kovach says when Okkhoy arrives.

Real life sometimes does not live up to the movies.

There are no scenes of an indebted Okkhoy running up and bearhugging Kovach. He is delighted at the suitcase full of toys the businessman has brought for him, but he is too tired and jetlagged to show it.

His father, too, is weary from the 17-hour flight -- and wary about these strangers' motivations.

The next day, as the Kovachs' take the family sightseeing, Abed decides to ask the question that has gnawed at him.

"I have only one question: Why are you doing this for us?" he asks in Bengali.

"Because I love him," Kovach says through a translator. "I felt his grief, I felt his pain and I just wanted to do something. I mean, if it was me, I was hoping somebody else would do the same thing for me."

As he speaks, Abed quietly listens. Tears well in his eyes.

"Thank you, thank you," he says in broken English.

The two men hug.

"It's just what we do," Kovach says. "It's just what we do as human beings."

Tears dried and the tension resolved, Abed relaxes and enjoys the day with his son.

They've been through a lot -- and a lot more lies ahead.

Devastating news

For a boy who spent three months in a hospital, Okkhoy is surprisingly at ease at the Children's Center.

He is struck by the contrast. It is clean, colorful, quiet -- the opposite of the grime and the stench of the medical facility he has been to.

"My heart is fluttering like a butterfly," he says.

For Abed, the surroundings mean little if the surgery isn't successful. And he has a clear-cut measure for success: Will my son be able to father children?

During the pre-surgery consultations, he poses the same question over and over to each doctor.

And each query is met with the same guarded response: That's the great unknown.

"We've seen young men coming back from Iraq who've been injured with rocket-propelled grenades and other things more severe than this," Gearhart says. "But just as far as an injury committed by one person against another, to a child, this is the most severe genital injury that I've ever seen in 23 years of doing this."

He admits the surgery won't be easy.

"This is an operation that is not in the book anywhere," he says. "We'll sort of develop this operation as we go along."

He's enlisted the help of two other doctors: Dr. Richard Redett, a pediatric plastic surgeon; and Dr. Dylan Stewart, a pediatric trauma surgeon.

The doctors plan to take tissue from Okkhoy's forearm -- between his elbow and wrist -- and reconstruct it into the shape of a penis. They will then transplant it down to the groin.

It'll look like a normal penis, Redett says -- but it won't be fully functional. The hospital MRIs have revealed the attack has left little penile tissue around the injury.

"The bad thing about the operation is he won't be able to get an erection without having something put in there when he is older," Redett explains.

The information is translated.

Shocked and in disbelief, Abed asks the doctor to repeat himself. He wants to make sure he understands exactly what the doctor said.

"When he's of age and he's ready to start a family, what did you say he will need?" he asks.

The boy will have to be flown back to the United States, Redett says, so that doctors can put in an implant that will allow him to have an erection.

And even after that, he adds, Okkhoy will need the help of a fertility doctor to successfully procreate.

The news devastates Abed.

He had hoped this trip to Johns Hopkins would make everything okay, because so much of Okkhoy's life isn't.

Abed, a rickshaw puller, sold his rickshaw and his home to pay for his son's medical treatment in Dhaka. His family is in hiding. He is in debt.

He knows there will be no return trip. Reality won't allow it.

When the family returns to the townhouse, Abed lets loose.

"Plastic surgery? Plastic surgery? We came all the way here for a cosmetic surgery that won't fix anything?" he testily asks Khan, the human rights lawyer.

Khan ponders for a minute what to say. What can possibly make up for a father's dashed expectations?

"Have faith in God," she finally says. "God has grand designs for your son."

A trial awaits

Back home, a difficult trial awaits -- one in which Okkhoy will eventually have to take the stand and relive, second by excruciating second, what was done to him.

"We hope that there will be some appropriate punishment," says Sohail, the battalion commander. "An exemplary punishment for these criminals so that the rest of the country knows."

The gang, according to battalion officials, has maimed at least five other children -- all of them around Okkhoy's age.

One of the men who confessed told investigators how the gang kept the kids confined for months in tight spaces or even in barrels and deprived them of food.

Then they'd send them out to beg.

Each child would bring back the equivalent of about $7 a day. The gang kept all but 25 cents of each haul.

The kids received mere pennies to feed themselves.

Were it not for Okkhoy, the enterprise would carry on.

"He's the only witness, the only witness who saw everything with his own eyes," Sohail says. "Without his statement, without him testifying in court, the case cannot be won."

Okkhoy's testimony is crucial for another reason.

The battalion has a reputation for coercing confessions, and human rights groups have long accused it of heavy-handedness in dispensing justice.

The U.S. State Department's latest report on human rights in Bangladesh accuse the battalion of using "unwarranted lethal force," and the government of withholding figures on how many extrajudicial killings it has committed.

Sohail, the battalion commander, sees it differently.

"The human rights activists and our style of work may be different but the goal is the same: to protect the human rights of innocent victims," he says.

The big day

It's the morning of the surgery, and Okkhoy is up before the sun. If he's nervous, he doesn't show it.

He makes faces at the staff, and tries to impress them with the English he's learned since arriving six days ago. "1, 2, 3, 4," he counts, holding up his fingers.

It amazes everyone who meets him.

"For a boy who's been through this kind of trauma, and seen this many doctors, I can't believe he's not scared of hospitals, he's not scared of doctors," Gearhart says.

As he is wheeled into the operating room, Okkhoy flashes a thumbs up.

As he is laid on the table, he chants, "Go, let's go!"

"Be brave," his father urges. "Don't be worried."

"I'm not," he replies. "I have no fear!"

Beep, beep, beep, the machines whir.

It's 9 a.m. and a team of doctors and nurses are preparing for a complicated operation that could take eight to 10 hours.

Outside, Abed paces back and forth, his arms crossed behind him, his head bowed.

It is the second time he has had to see his son in a hospital and he is clearly nervous.

He calls his wife back in Bangladesh.

"The surgery will go on all night," he tells her. "Get a megaphone and tell the whole neighborhood to pray for him. It is now in God's hands."

He checks his watch. It's only 9:05 a.m.

Beep, beep, beep.

Inside the OR, Gearhart readies to make the first incision.

What the doctors are hoping is that Okkhoy was left with enough of his own penile tissue, hidden inside his body, that they can pull out.

The tests they did earlier in the week suggest there isn't. But MRIs have been wrong before.

Everything now rests on what Gearhart finds.

"So, let's have a look," he says.

A few short minutes go by.

Gearhart: "I'll tell you, Rick, I'm getting a little more encouraged, you know? I really am."

Redett: "The good thing is, it's sensate too."

Gearhart: "It's sensate, absolutely! The good Lord made this one sensate.... Can we have a ruler? Yeah! Good for him. Good for him!"

Exactly 34 minutes after he walked into the operating room, Gearhart walks out -- and heads straight for the waiting room.

"So we have some wonderful news. Wonderful news," he begins.

In males, part of the penis is held inside the body, tucked up inside the pelvis and attached to the pubic bone. Think of a tree where we only see the part above ground; not the root hidden below.

Read more: Penile surgery explained

"After we took all the scar tissue away and after we took all the skin away, we actually found that there is a reasonable amount of penis down, submerged under the skin, under the scar, that's usable," Gearhart says.

"So, therefore, we're not going to have to make him a new penis."

The doctors also found they would be able to move the urethra -- the tube used for urination -- to the tip of Okkhoy's penis. Translation: He will no longer have to relieve himself from the tiny hole the doctors in Bangladesh bore.

"Oh very good news! Very good news!" Abed exclaims.

Abed soon learns there are even more reasons to celebrate.

The penile tissue is "sensate," meaning Okkhoy will be able to have sensations and erections. And the tissue will cause his penis to grow as Okkhoy grows.

Abed can't hold back tears.

"Hey Allah," he sighs with relief, thanking God.

Khan too cries. She's been by the family's side for more than a year now, fighting for Okkhoy.

"All these months, all the worry. All this has borne fruit," she says.

Instead of 10 hours on the operating table, the surgery takes less than three.

Redett's team uses skin from Okkhoy's thigh for the shaft of the penis and tissue from his inner cheek lining to create the glans, or tip.

"It couldn't have gone better," he later says. "Absolute best solution. "

A promising future?

Children are resilient, so Okkhoy's recovery is quick.

He is discharged from the hospital less than a week after the surgery, but needs to remain in the area for three more weeks so doctors can monitor him for infections.

He is restricted from physical activity -- which means, he can't kick his beloved soccer ball around.

That leaves Okkhoy without an excuse when Khan sits him down to tutor him from a picture book of alphabets.

"A. B. C. D," Khan points to the letters and reads aloud.

"A, B, Chi ...," Okkhoy repeats.

"Not Chi. Say 'C,'" she corrects him.

Khan wants Okkhoy to be the first person in his family to get an education.

"The dream I have for him is that he grows up and devotes his life to the service of people," she says. "That he sees to it that no one goes through what he went through."

It is a dream Kovach and his wife share as well. The two want to set up a fund to help make Okkhoy's schooling possible.

Before he leaves Baltimore, Okkhoy is asked again what he wants to be when he grows up.

Until now, his answer had been the same: a member of the Rapid Action Battalion to avenge his attack.

Not this time.

"I want to become a doctor," he says without missing a beat, "because I want to save people. "And when I do, I won't take any money from them."

A hospital staffer suggests that perhaps one day Okkhoy could come work as a surgeon at Johns Hopkins.

"Wouldn't that be a miracle?" she says.

"This story is full of miracles," Okkhoy's father responds.

Who's to say there won't be another one?

Click here to find out how you can help