The International Committee of the Red Cross has begun a major conference in Geneva on the problem of the millions of people who go missing during armed conflict.
The meeting, which brings together 350 experts from 90 different countries, will try to revitalise efforts to find out what has happened to those who have vanished and will set out practical guidelines for preventing disappearances in the first place.
If you know that your family member is dead you can accept it. But not knowing, and waiting every moment of the 24 hours of the day, waiting for the return, it's very, very difficult
It is an obligation under international humanitarian law for all warring parties to investigate what has become of anyone who is reported missing during hostilities.
In practice, however, that is rarely done.
Authorities frequently block efforts to research disappearances, fearing that they may stir up ugly ghosts of the past which could hinder peace settlements.
At the conference, the families of those who have vanished are insisting they have a right to be told the truth.
One of the speakers is Visaka Dharmadasa, whose son Achintha disappeared in Sri Lanka in 1998.
She says until she is sure of what has become of her son, she cannot get on with her own life.
"If you know that your family member is dead you can accept it. You grieve, you mourn, then go back to your day-to-day business," she says.
"But not knowing, and waiting every moment of the 24 hours of the day, waiting for the return, it's very, very difficult."
The Red Cross hopes the three-day conference will force authorities to face up to their legal obligations and to do all they can both to explain past disappearances and to prevent future ones.
It is also suggesting a series of practical measures to reduce the numbers of missing, including the simple requirement that all soldiers going into battle should wear identification discs, whether they are from national or rebel armies.