Geneva, Switzerland - Fatima Khan's voice pierces the silence of Geneva's chilly streets as she runs after officials from the Syrian government delegation.
"Why did you kill my son?" she screams. "Tell me, why did you kill my son?"
She receives no answer. The officials walk away in haste, taking long steps while keeping their heads down until they reach a parked black Mercedes and are driven away.
Fatima Khan came to the Swiss city from Britain to seek answers as to why her son Abbas Khan, a British doctor, died in a Syrian government-run prison in Damascus.
She says Abbas was a humanitarian worker who travelled to Syria for voluntary work before he was captured and put in jail.
His death was announced in December, just a few days before his scheduled release.
The Syrian government says he committed suicide in prison by strangling himself with his pyjamas. Fatima Khan accuses the regime of killing him.
She knows that coming to Geneva will not bring her son back. She knows that she will never get satisfactory answers.
But she still chased the Syrian delegation through the streets, in the hotel lobbies - and even at the UN headquarters where negotiations between the Syrian government and the opposition were taking place.
"I want to embarrass them in front of everyone. Maybe they will now think twice before killing anyone in detention, maybe this will save another son's life," she told Al Jazeera as she tried to hold back tears.
The Syrian authorities are accused of holding tens of thousands of political detainees. New York-based Human Rights Watch says arbitrary detention and torture has become "business as usual for Syrian security forces".
Just a few days before the Geneva talks, a report emerged purporting to show evidence of systematic torture and killing of about 11,000 detainees.
The Syrian government officials on hand in Geneva denied the authenticity of the report. They said the images were fabricated by "the hostile" country of Qatar, which had commissioned the report.
I want to embarrass them in front of everyone. Maybe they will now think twice before killing anyone in detention, maybe this will save another son's life.
The fate of Syria's detainees became a recurring topic as journalists confronted government officials at the peace conference.
In the media bar of the UN headquarters in Geneva, as Omran Zoabi, the Syrian information minister, leisurely sipped coffee in the company of a group of journalists, a reporter seated next to him asked: "What happened to Abdel Aziz al-Khayyer?"
Al-Khayyer, a prominent Damascus-based human rights activist, has been missing for more than a year. His opposition group, the government-tolerated National Coordination Body, has accused the intelligence services of detaining him.
Answering the reporter’s question, Zoabi said: "You are talking about my friend, Abdel Aziz al-Khayyer. He is a friend.
"Even though we had differing views, we used to be driven back from conferences in the same car."
Zoabi continued: "I want him to be free. He wasn't arrested by the Syrian authorities. If we had information about his whereabouts, we wouldn't have waited until this noise happened."
Another journalist in Geneva asked Faisal Maqdad, the Syrian deputy foreign minister, about a list of tens of thousands of names of detainees provided by the opposition to the UN.
Maqdad said: "When we examined the list, we found that 60 to 70 percent of the people in it have never been in prison. Twenty percent were people freed from prison [already]. And the rest, we don’t know anything about them."
Reacting to a claim made by a journalist and echoed by human-rights organisations, Maqdad said: "We do not have children detainees."
Fate of detainees
The negotiations between the two rival Syrian delegations were based on a communique from 2012 that lays out a political transition plan and calls for the creation of humanitarian corridors and the release of detainees.
For those whose family members are believed to be held in prison, nothing could be more ominous than the government's denial of the existence of their loved ones.
What you see in Geneva, it's just a theatrical play. The world is pretending to be doing something for Syria but they are wasting time.
The sister of Ahmad Hilmi does not know the fate of her 25-year-old brother. Ahmad, a Red Crescent volunteer, was detained about 20 months ago.
"We continue to hear mixed reports. Some say he is still alive, while others told us he died under torture," she told Al Jazeera.
She was never optimistic that the peace talks in Geneva would lead to the release of her brother - or any of the other detainees.
She blames the international community for its "lack of seriousness" in putting pressure on President Bashar al-Assad's government.
"What you see in Geneva, it's just a theatrical play. The world is pretending to be doing something for Syria but they are wasting time," she said.
Adnan Haddad, a young Syrian activist, came from the war-torn city of Aleppo to observe that play in Geneva.
He sat in the press room watching the Assad government official as he dismissed the opposition-provided list of detainees as inaccurate.
"I'm not surprised," Haddad told Al Jazeera.
"If the regime admits to the presence of detainees, it would be condemning itself in front of the international community.
"This is simply because the regime killed a lot of them under torture. The rest of the detainees will be used as a bargaining chip."
Justice for all
Sitting at the doorstep of the entrance to the UN building in Geneva in freezing weather, Fatima Khan screams to passing crowds that she wants justice for all the detainees still alive in Syria.
"We are living in a civilised world and still the international community allows the Assad regime to get away with crimes," she says.
Fatima Khan was allowed by Syrian authorities to visit her son in prison several times during her five-month stay in Damascus as she tried to secure his release.
She said Abbas looked as malnourished as some of the men pictured in the report about detainee abuse.
"They starved people. He told me they tortured people for pleasure. How can we allow that?" she said.
On the day Fatima Khan thought she was going to meet her son upon his release, she brought the guards chocolates and sweets to celebrate.
"They told me my son committed suicide - while chewing the sweets I had given them."
Follow Basma Atassi on Twitter: @Basma_