CAIRO - State security came for Philip Rizk on Friday night. He had just finished a six-mile protest walk with about 15 friends to raise support for Palestinians in the Gaza Strip when he was detained for hours and then hustled into an unmarked van and driven off. He has not been seen or heard from since.
For two days the authorities denied that he was being held. Then on Sunday, at 10 p.m., a security official at the American University in Cairo, where Mr. Rizk studies, was able to confirm his arrest to his family. His mother and father tried to get some sleep, but at 1 a.m., security agents showed up at their door, five plainclothesmen and two guards carrying automatic weapons.
After searching their apartment, the security agents tried to take his father, Magid, away, too. He refused to go, and the authorities backed off when representatives of the German Embassy and Amnesty International arrived in the middle of the night. Philip Rizk's mother, Judith, is German, and he has dual Egyptian-German citizenship.
"It's like a bad movie," Mrs. Rizk said.
The war in Gaza has left its mark in Egypt. The authorities here have been increasingly frustrated with criticism at home and abroad for refusing to fully open the border between Rafah and Gaza.
Now, according to the accounts of five witnesses to Mr. Rizk's arrest, and interviews with his parents, his sisters, human rights lawyers and some of his professors, it appears that the Egyptian authorities have turned to the country's emergency law to silence criticism of its Gaza policy. The law, adopted to combat terrorism after President Anwar el-Sadat was gunned down in 1981, allows the government to detain people without charge and effectively eliminates any right to due process.
The government acknowledges holding about 1,800 prisoners without charge under the emergency law, but human rights groups say the number could be closer to 10,000. The law is routinely used against members of the Muslim Brotherhood, a banned but tolerated social and political movement. Dozens of Brotherhood followers have been arrested since the start of the Gaza conflict.
"Officially, nobody knows where Philip is," said Hassiba Hadj Sahraoui, deputy director in the Middle East and North Africa for Amnesty International. "Philip has disappeared."
A spokesman for Egypt's Interior Ministry, which handles all matters of internal security, was furious at being asked about the case. The spokesman is a general, but talked only on the condition that he not be identified by name because of the security nature of his work. He declined to answer questions, and said: "This happened within the framework of the Egyptian law. You can go to the office of the general prosecutor. I have no information about Philip. Who said they don't know where he is? What is the secret behind the interest of The New York Times in Philip? Are you working for human rights organizations?"
The general was angry; the Rizk family was terrified.
Judith and Magid Rizk live in a small, neat apartment, in a rare quiet section of Cairo. Mr. Rizk is a small book publisher, a man who wears starched white shirts and sweater vests. He is not a political man. But he said he supported his son's interests in social causes. "This is his niche, his passion," Mr. Rizk said. He does not want to antagonize the authorities. He said he just wanted his son back in time for his birthday.
Philip Rizk turns 27 on Thursday.
"We don't know where he is; we have not talked to him. We don't know if he is eating, if he is sleeping; we don't know what they are doing to him," Mrs. Rizk said. She was tired, scared and, after having lived her adult life in Egypt, stunned that men with machine guns and riot gear had come to her door. The family started a Facebook page to gather and publicize pleas for his release.
Mr. Rizk appears tall and thin as he walks through the scenes of a 28-minute movie he made, "The Palestinian Life, Village Stories." After he graduated from Wheaton College in Illinois with a degree in philosophy, he moved to Gaza to work with an Anglican charity. He lived there for two years, and during that time made his rather somber documentary of average Palestinians trying to survive. "I found that because violence makes news, the stories of ordinary people never get out," he said in the introduction. His film, he said, celebrated samud, or the steadfastness, of the Palestinians.
When he returned to Cairo, he enrolled in a master's program in Middle East studies at the university. He also joined a group in Cairo called the Popular Committee in Solidarity With the Palestinian People. It was a left-leaning group of mostly young activists. About a month ago, the group decided to stage a symbolic march to Gaza. About half of the participants were Egyptian and half foreign.
The group met Friday morning and took a bus north from Cairo to the Qalyubiya governate, an hour away. The demonstrators walked for about two hours, waving Palestinian flags and talking with local residents.
Mr. Rizk carried a handwritten sign in Arabic reading: "We are fed up. Open the Rafah border."
When the walk was over, the marchers climbed into small buses or their own cars for the ride back to Cairo and were quickly detained. Witnesses described being surrounded by large numbers of police officers for about four hours and being promised that everything was routine and that they would be released soon. A human rights lawyer arrived. The marchers were taken to a local police department and told that their passports would be copied and that they would then be released.
At that point, the police asked to speak to Mr. Rizk. After some negotiating he agreed to enter the police station with the lawyer, but the police distracted the lawyer and hustled Mr. Rizk out a back door. He managed to phone his friends, who said they threw themselves in front of the van he was in, but were pulled off by the police. Three members of the group chased the van in their car for more than half an hour, until they were stopped at a roadblock.
Security police officers started visiting the homes and offices of other young people involved in the trip. Sarah Carr, a dual British-Egyptian citizen and reporter for the English-language Daily News, who covered the event, was too afraid to go home, or to work after hearing that the police had inquired about her. Katharine Hall, 20, of Britain, was sitting in a cafe in downtown Cairo when her roommate phoned to tell her that the police had come to their door. "I don't know where I'll be, and I am not telling you," Ms. Hall said as her cheeks flushed red. "They are trying to scare me. So I don't want them to find me." She left the cafe.
On Sunday, about 50 students and faculty members at the American University in Cairo's campus held a small demonstration calling on the authorities to release Mr. Rizk. The signs they held up said, "Where is Philip?"