The Syrian mothers forced to trawl photographs of the dead to find out if their sons and husbands are alive

At least 70 people (20 of them children) were killed in a suspected chemical weapons attack on a rebel-held Syrian town earlier this month. US President Donald Trump has now responded via missile strikes on a Syrian air base. He condemned the deaths of innocent civilians, with Pentagon spokesman Captain Jeff Davis calling the air strikes "proportional response to Assad's heinous act".

The Telegraph hears from a Syrian mother who knows all too well the horror of not knowing whether your child is dead or alive. Miriam Alhallak was part of a documentary released last month which heard from Syrian families who have been forced to scroll through pictures of corpses in the hope of finding their loved ones who have died in the regime's clandestine prisons. Here, we tell her story.

Mariam Alhallak's son Ayham was her treasured boy. He was her miracle baby, who had arrived late in her life at a time when she and her husband had worked hard to hold down stable jobs - she as a headmistress and he as a teacher - in order to buy their own house in a village outside Damascus. Watching Ayham grow from a happy little boy into a feisty, intelligent young man, destined to become a doctor and make his family proud, was one of the great joys of her life.

But by the time Ayham was 25, Mariam's world had been ripped apart. Ayham - who had flourished at school and university - had become increasingly angry about the reign of terror President Assad's regime was inflicting on his country, and like many young Syrians joined the uprising in the wake of the Arab Spring in 2011.

A year later, Ayham began working for a human rights organisation called the Syrian Centre for Media and Freedom of Expression, which was documenting the thousands of arrests and disappearances of Syrian citizens. By that time, detention was a longstanding tool of repression used by the state to silence and punish its critics, but it was now being used on a vast scale.

Ayham was arrested in February of 2012. Within 24 hours, Mariam's son had become one of the tens of thousands of Syrians "missing in detention", punished for opposing the Assad regime and detained at an undisclosed centre, with no way of telling whether he was dead or alive.

For Mariam, the waiting was unbearable. She managed to find out which detention centre Ayham had been sent to, and went there regularly for 66 days asking the unfeeling men guarding the gates when he was going to be released and if she could see him.

"Ayham's share of the beatings was on a daily basis," she says, "first of all because he was a doctor, and secondly because our village is very loyal to the president. When he was moved to a prison where he could have visitors, he had become so thin I couldn't control myself when I saw him. 

"When he was finally released 21 days later, he had scabies and had been beaten everywhere, especially on his kidneys. 

"He didn't talk about the torture. After he came out he didn't speak at all. He had nightmares when he slept. I saw how he woke terrified."

Mariam was relieved to have her broken boy home, but the family's trauma was not over yet. Six months after he was released, Ayham was arrested again. This time, he never came home. 

This is the hidden horror of the six-year-old Syrian civil war. A new Channel 4 documentary - Syria's Disappeared: The case Against Assad - has investigated how President Bashar al-Assad's regime continues to detain people, refusing to disclose any names or acknowledge how many people are being held in its clandestine prisons. Using testimonies of survivors and evidence smuggled out of Syria, the film follows victims, family members and international war crimes investigators as they campaign for the release of the disappeared and fight to bring the perpetrators to justice. ​

For the families and friends of those detained, this is another form of torture. They search for news about their disappeared loved ones daily, not knowing whether they are dead or alive. There is one way to find out, but it is so unremittingly chilling it makes your blood run cold.

The Assad regime is meticulous in its documentation of the horrors it unleashes on innocent people. Photographs taken by the military police catalogue those who have died while being detained. Thousands of these photographs were smuggled out of the country in 2013 by a defector codenamed Caesar.

They show more than 6,700 corpses of people who died in the custody of the regime. Scrolling through the images is truly distressing - many of the bodies are emaciated and show clear signs of torture, with bruises, burns and eyes gouged out. They are numbered and photographed with a card recording which detention facility they died in. 

This is how Mariam finally learned the truth about what happened to Ayham. A year and a half after her son was detained the second time, Mariam was finally given some information about what happened to her son.

"Every day or two I would make the trip to the Palace of Justice and submit requests to the Military Police and the Military court," she says.​ "Three months passed like that, waiting for him. Perhaps inside me I felt that something had happened to him. 

"I still hoped that he would be released, but after three months passed, we received news.

"I was at home with friends when my sister arrived. Straight away I shouted “Has something happened to Ayham?” She said 'Yes.'"

Mariam was told that a young man who had been arrested with Ayham had been in touch with a family friend to say that they had both been tortured and that though he had survived, Ayham had died five days after entering the prison. 

Mariam and her husband were distraught. But 20 days later, they received the news that Ayham was still alive. Mariam was determined to find out the truth. Was her son, who she had spent the past three weeks mourning, dead or alive?

Every two weeks for a year and a half Mariam went to the Palace of Justice to submit a request about the whereabouts of her son. Finally, an assistant began to feel sorry for her, and one day handed her a piece of paper with the words "Corpse 320" written on it. "I then looked at the dates," she says, "it appeared they had received the news of his death on November 21 2012, and he had died on November 11 2012.

"So he had died within a matter of days of his arrest, and I had been coming there for a year and a half."

Mariam battled to get her son's body or even his belongings returned to her to no avail. Months later, when the Caesar photos were published, a family friend searched through them and found a picture of Ayham. 

"I saw the photo and felt a great sense of relief. Because it was confirmation. Because they were his last moments. Because we didn't see his body. 

"Now, I carry it with me on my mobile always."

A picture of her dead son is, for now, all Mariam and her family have in lieu of his body. One day, she says, she hopes she will be able to give him a proper burial.  "If he is buried in mass graves there is hope that Bashar Al-Assad will be prosecuted in the future and that we can find his DNA, but if it’s true that they are destroying the bodies then it’s very difficult."

Mariam is haunted by the knowledge that Ayham was tortured before his death. She will not rest until she has brought his body home. "I want a grave for my son," she says.

"Sometimes I remember the nice things. I miss sitting down with him in the mornings. We used to sit together drinking coffee and listening to a singer called Fairuz.

"Anything, everything reminds me of him."

Syria’s Disappeared: The Case Against Assad was on Channel 4, Thursday 23 March, 10pm, and can be found here on 4od.