The names in this report have been changed out of security concerns for Yazidi family members still being held by ISIS.

Duhok, Iraqi Kurdistan (CNN) The children laugh and shriek, as some of them seem to always have the capacity to do no matter how depressing the circumstances.

Their bright clothes provide splashes of color against the otherwise drab monotone white of the endless rows of tents.

A small group plays with rocks, replacements for the toys they left behind when they fled, while others clamber through a jagged tear in the wire fence surrounding the refugee camp.

The Shariya refugee camp opened around six months ago, made up of some 4,000 tents and counting.

Thousands of Yazidis now call this corner of Iraqi Kurdistan home, about 18 miles (30 kilometers) from one of the front lines with ISIS , where one can hear the occasional reverberation in the distance of what we are told are airstrikes.

The Yazidis have long suffered persecution, with many Muslims referring to them as devil worshipers. The ISIS storming of Sinjar created a humanitarian crisis as some fled into the mountains and were trapped without food or water.

The Yazidis have long suffered persecution, with many Muslims referring to them as devil worshipers. The ISIS storming of Sinjar created a humanitarian crisis as some fled into the mountains and were trapped without food or water.

No one knows the reason why, but in early April, ISIS released more than 200 Yazidis . Many of them were women and children, others were ill or elderly.

Many families were separated when ISIS forces raided Yazidi villages, mercilessly killing anyone who tried to escape.

Many families were separated when ISIS forces raided Yazidi villages, mercilessly killing anyone who tried to escape.

Despite everything they've been through, some Yazidi refugees find a reason to smile.

Despite everything they've been through, some Yazidi refugees find a reason to smile.

A man gives another a shave. For many, an element of normalcy has returned after months in the camp.

A man gives another a shave. For many, an element of normalcy has returned after months in the camp.

A small child is seen within the safety of a tent at the refugee camp. It's not known how long they'll have to stay here.

A small child is seen within the safety of a tent at the refugee camp. It's not known how long they'll have to stay here.

The Shariya camp opened six months ago and now 4,000 tents line the dusty ground, providing shelter to thousands of refugees.

The Shariya camp opened six months ago and now 4,000 tents line the dusty ground, providing shelter to thousands of refugees.

Children play in the dirt with toys crafted from cardboard. Some clamber through the wire fence and play with rocks -- anything to keep themselves entertained.

Children play in the dirt with toys crafted from cardboard. Some clamber through the wire fence and play with rocks -- anything to keep themselves entertained.

Amid all the uncertainty, a woman carries out domestic tasks. Yazidis are of Kurdish descent, and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism.

Amid all the uncertainty, a woman carries out domestic tasks. Yazidis are of Kurdish descent, and their religion is considered a pre-Islamic sect that draws from Christianity, Judaism and Zoroastrianism.

While thousands of Yazidis were captured, thousands of others fled. Many ended up here in the camp, where you can hear the occasional reverberation of what are said to be airstrikes from the ISIS front line, around 30 kilometers (18 miles) away.

While thousands of Yazidis were captured, thousands of others fled. Many ended up here in the camp, where you can hear the occasional reverberation of what are said to be airstrikes from the ISIS front line, around 30 kilometers (18 miles) away.

Thousands of Yazidis from the town of Sinjar were taken captive by ISIS forces. Fighters separated the women from men and forced them to become sex slaves. Men faced a choice: Convert to Islam or be shot.

Thousands of Yazidis from the town of Sinjar were taken captive by ISIS forces. Fighters separated the women from men and forced them to become sex slaves. Men faced a choice: Convert to Islam or be shot.

A small boy sits on the ground at Shariya refugee camp in Duhok, in Iraqi Kurdistan. It's home to thousands of Yazidis, many who fled from Mount Sinjar and surrounding towns when ISIS fighters moved in.

A small boy sits on the ground at Shariya refugee camp in Duhok, in Iraqi Kurdistan. It's home to thousands of Yazidis, many who fled from Mount Sinjar and surrounding towns when ISIS fighters moved in.

Thousands taken captive

The vast majority of the camp's occupants are from the town of Sinjar, which is near the border with Syrian Kurdistan, and fled the ISIS assault there back in August. But not everyone escaped. ISIS took thousands of Yazidis captive.

The fighters separated the young women and girls, some as young as 8 years old, to be sold as slaves, for their "masters" to use as concubines. Men faced a choice: Convert to Islam or be shot.

Mahmoud was out running errands when ISIS fighters arrived, taking his wife, Ahlam, their three children -- the youngest of which was just a month old -- and his elderly parents.

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"They took our phones, jewelry, money," Ahlam recalls. "They had guns. They forced us at gunpoint into big trailer trucks."

They were taken to a school turned prison in Tal Afar. From there, the family was moved from village to village -- and at one stage taken to Mosul.

"They wrote everyone's name down and they asked where we want to work, in the fields, as cleaners or as herders," she says.

Ahlam and her family chose to herd goats.

They were then taken to a Shia village whose residents had fled, where they were part of a group of around 40 living in one house. In the home, Ahlam found a cell phone left behind by its former occupants and called her husband.

We sometimes say that we wish we had been massacred. This would be better than being kidnapped and raped. Vian Dakhil, Yazidi lawmaker

"I said we are alive but we are prisoners."

Ahlam's husband, who up until that moment had lost the will to live, thinking his family was dead, says he cried out of happiness despite his pain.

Ahlam would call when she could, briefly, after midnight, hiding under her bedcovers. If she was caught with a phone, she would be killed.

Village prison

The village itself was a massive prison, its entrances guarded by ISIS fighters.

She recalls that two men, in their late 40s or 50s, tried to escape. When they were caught, their bones were broken, their bodies tied to the back of a truck and then driven through the streets.

The Yazidi captives were forced to watch the gruesome spectacle. The men's corpses were then tossed into a ditch and an order given not to bury them.

One night, some of the Yazidi men risked their lives to toss dirt onto the bodies, to give those slain what dignity they could.

Ahlam tells us that about a week before we met, ISIS fighters came by and took away her in-laws and the other elderly people living in the house.

"We didn't know where they were taking them, we thought we would be next," she remembers.

So she and the rest of the group realized that they had to try to flee.

"We decided that either we survive or we don't."

Escape attempt

They left at midnight. Ahlam cradled the baby, as her two other children, ages 3 and 4 years old, clutched at her clothes. She prayed the baby wouldn't cry, that the children could keep walking.

They knew the general direction to take, but not the exact route, and they could only hope it was toward freedom.

"When the sun started to come up, I thought that's it, we are going to get caught," Ahlam says. "And what am I going to do with the kids? I can't carry all three of them and run."

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Luckily, Ahlam never had to answer that impossible question. The group made it into Iraqi Kurdistan.

The couple can't put into words their emotions when they were reunited.

Mahmoud, gently caressing his daughter's palm, says he could hardly believe that the woman whose stunning eyes and gentle words he had fallen in love with, and their three children, were by his side again. It had been eight agonizing months.

But their joy was tainted by fear for Mahmoud's parents.

A few days after Mahmoud and Ahlam were reunited, ISIS released 217 captives.

No one is disclosing exactly why. Among them were 60 children, a handful of men and women, and the rest were elderly -- including Mahmoud's parents.

"We didn't know if they were going to slaughter us or what they were going to do with us," Mahmoud's father says.

"They moved us around a lot, and at one stage we stayed in in one place for three days."

But Ahlam's parents are still with ISIS.

Haunted by screams

Vian Dakhil, a Yazidi member of Iraq 's parliament, speculates that the Yazidis ISIS released are individuals they were struggling to care for.

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Dakhil is part of Iraqi Prime Minister Haider al-Abadi's delegation to the United States this week. She will be addressing the United Nations -- pleading for more international support for Iraq and more airstrikes to help defeat ISIS -- and she will address the plight of the Yazidis.

"We sometimes say that we wish we had been massacred. This would be better than being kidnapped and raped. We prefer death now over the fate of what is happening to these girls and women," Dakhil says.

"It is now on the government and on the international community to focus on this. How to get these captives back. It's inconceivable that in the 21st century, something like this is happening as if we were living in the Stone Age."

Ahlam says she was spared because she was breastfeeding and she had young children, which, we're told, makes her impure and therefore unable to be used as a sex slave.

For Ahlam, what she went through was not the hardest part of her ordeal.

It's the moment when the ISIS fighters began taking away the girls and young women. She's haunted by their screams, the image of them being dragged away sobbing and screaming.