By Daniel Schweimler
BBC News, Buenos Aires
There have been demonstrations in the Argentine capital, Buenos Aires over the disappearance of Julio Lopez , a bricklayer who went missing after testifying in court that he had been tortured during the country's military dictatorship in the 1970s and 1980s.
Julio Lopez last seen on 18 September
"Where is Julio Lopez?" is the question hanging over Argentina.
It is on banners and posters on buildings across the country, it has been texted to every mobile phone user and President Nestor Kirchner has taken a personal interest in the case, meeting the family.
The 77-year-old former labourer was last seen on 18 September. There has been no trace of him since.
It could be that Mr Lopez, who suffers from Parkinson's disease, was confused and under pressure and he simply wandered off. But most suspect he has been kidnapped and possibly killed by supporters of the military government in power in Argentina between 1976 and 1983.
Julio Lopez had been detained and tortured under that government. He told his story at the trial earlier this year of the former police chief, Miguel Etchecolatz who last month was sentenced to life in prison for kidnap, torture and murder.
It was the first major trial of the leaders of that military government since the Argentine Supreme Court last year overturned amnesty laws that had allowed them to walk free.
Mr Lopez was one of 30,000 people detained and tortured under the junta
Now those ageing generals and police officers fear they may be following Miguel Etchecolatz back to prison.
After the disappearance of Julio Lopez, it came to light that other witnesses in the trial had been threatened - tape recordings of people being tortured were sent to some.
The judges in the case, the lawyers, journalists and human right activists also received menacing letters and e-mails.
It seems as though "The Dirty War" - as the period of military repression became known - is not yet over.
Show of defiance
On the other side of the political spectrum, the families of the soldiers, policemen and prison officers killed by left-wing guerrillas in the 1970s held a rally in the centre of Buenos Aires demanding that their loved ones also be remembered.
But some at the rally turned it into a show of defiance, a defence of a military government that most Argentines see as indefensible.
The last leader of that government, Reynaldo Bignone, sent them a message of support urging activists to, as he put it, finish the work that the military could not. He later claimed his words were taken out of context. But few Argentines doubted what he meant.
When democracy returned in 1983, several leaders of the repression were tried and sentenced to long jail terms for the kidnap, torture and murder of an estimated 30,000 people.
But those early civilian governments then passed laws which allowed the guilty men to walk free.
Some said it was simply time to put the past behind them, others believed they had acted under pressure from a still powerful military.
It was mostly the leaders who were tried.
The men who drove the unmarked cars in the middle of the night to drag students from their beds, the torturers who applied the electric cattle prods, the doctors who stole new-born babies from mothers who were then killed and the pilots who dumped the drugged but still living bodies into the River Plate were generally allowed to go free.
Living in Buenos Aires I cannot help wondering to this day whether that middle-aged taxi-driver, that harmless looking butcher, the moustachioed security guard may be a former kidnapper and torturer.
The survivors of those years of terror and the families of the victims have never given up the fight for justice.
The Mothers of the Plaza de Mayo still march every Thursday afternoon outside the government palace carrying placards bearing the photographs of their loved ones - demanding answers.
Mothers of the Plaza de Mayo march every Thursday afternoon
Another human rights organisation recently identified the 85th child stolen from its mother while in captivity and given for adoption to a childless military or police couple.
Those babies are young adults now. The activists estimate that several hundred babies were stolen and their work goes on.
All the surviving victims have had to cope in their own way.
I have met three, all of whom left a profound impression on me - for their resilience and their ability to overcome horrors that most of us can only imagine. All were tortured and lived every moment in captivity not knowing if it would be their last.
Daniel Acosta, an artist, tells his story through his work - pictures with a depth rooted in his suffering.
Claudio Tamburrini was strapped to a bed, naked for days on end. He and three colleagues escaped from their detention centre - a harrowing story told through his book and film, Chronicle of an Escape.
Adriana Calvo was pregnant when agents working for the military government kidnapped and tortured her. After several weeks in captivity she was suddenly released.
She believes it was to act as a witness to the horror that awaited anyone who dared to oppose the authorities.
She too was a witness at the Etchecolatz trial and she too received threatening phone calls.
Julio Lopez's son, Ruben, a carpenter, said the family was living in fear of what might have happened to his father but in their hearts hoped he would reappear safe.
For the rest of Argentina, the disappearance of Julio Lopez is a potent symbol of a battle not yet won.
From Our Own Correspondent was broadcast on Saturday, 14 October, 2006 at 1130 BST on BBC Radio 4. Please check the programme schedules for World Service transmission times.