It has been almost three weeks since Ziad Bakir disappeared.
For his family, it means long, anxious days of waiting and wondering.
"Believe me, everything came to our mind," says his father, Mohammed, at home in the neighbourhood of Mohandiseen.
"Perhaps he has been killed, he has been injured, he has been detained."
Mohammed says he visited all the hospitals and morgues of Cairo, looking for his son, but found nothing.
Ziad, a 37-year-old father of three, is a graphic designer with the Cairo opera. An artist not much interested in politics. But conscious, in late January, that something hugely important was happening.
His sister, abroad at the time, suggested he should go and take a look.
"I have a bit of a guilty feeling that maybe I encouraged him to join the demonstrations," says Mirette, also an artist.
On Friday 28 January, Ziad finally decided to take part. He asked for his father's advice. Mohammed hesitated but concluded it would be wrong to say no.
Accompanied by a friend, Ziad joined the demonstration in Tahrir Square, just as tensions came to the boil.
The square was thronged with demonstrations and there were ugly scenes as pro-Mubarak supporters attacked from nearby streets.
The friend left for a couple of minutes. When he came back, Ziad was gone.
During those chaotic days, hundreds of protesters were arrested, some by the police, and some by officers in plain clothes.
Most of those detained were released last week. But at least 100 remain in military camps. And around 50, including Ziad, are still unaccounted for.
Human rights activists are struggling to keep up with the aftermath, not helped by the fact that Egypt's new military rulers are saying nothing.
"I think it's one rule of human rights," says Ahmed Ragheb of the Hisham Mubarak Law Centre, "that the government... show how many people are in the camps in Egypt and why these people are in these camps."
With the army now in charge, there are real concerns that old regime habits remain very much alive.
"It's worrying that the military is still involved in these detentions," says Tom Porteous, of Human Rights Watch, "at a time when the military needs to send very clear messages about a break with the repressive past."
For Ziad's sister, the message so far has been confusing.
"We were expecting this to come from the police but not from the army," says Mirette. "Why did you detain my brother? What did he do?"
For all the nagging fear, her father Mohammed chooses to be hopeful.
"He will return back I'm sure," he says, stoically. "But looking forward for the future of this country, it is democracy, democracy, democracy."