Mr. Islam’s co-workers believe his case fits the same pattern, even as the authorities deny any involvement by security agencies. In July, Ms. Hasina seemed frustrated by the outside attention on the case, saying that suspicions about security forces were unfounded and that Mr. Islam’s image as a labor leader was misleading, since he actually worked for a nonprofit group. “Why don’t you inform the embassies of the Western countries that Aminul was not a workers’ leader?” she said, according to The Independent, a Dhaka publication.

One of the biggest mysteries in the case involves Mustafiz Rahman, the man who sought Mr. Islam’s help in arranging his wedding on the night that Mr. Islam disappeared. Mr. Islam’s co-workers say Mr. Rahman had ties to security forces, while an investigative account in the New Age, a Bangladeshi publication, said Mr. Rahman had helped the police arrest a different labor organizer and had been seen in the presence of intelligence agents.

He has not been seen or located since the day Mr. Islam disappeared.

Leaders of the biggest Bangladeshi labor federations have condemned Mr. Islam’s killing but also complained that the Solidarity Center and its unions initially shunned them and looked overseas for help.

“They didn’t do anything on the ground,” said Roy Ramesh Chandra, head of the country’s biggest labor federation, a government ally. “They have only asked for solidarity support from the outside. They only send e-mails that tarnish the image of the country, industry, even the trade union movement. That is not acceptable to us.”

This concern about national image is a major reason some of Mr. Islam’s supporters believe the government may have considered him a threat. He had documented his 2010 abduction and torture on a labor Web site. This year, he helped arrange interviews for an ABC News report about unsafe conditions at a factory where 29 workers died in a fire while sewing clothes for Tommy Hilfiger.

Mr. Islam lived in Hijolhati, a small, leafy village about an hour’s drive from the Ashulia factory district. His widow, Hosni Ara Begum Fahima, still lives in their simple concrete home. Mr. Islam has been reburied there, in the small dirt backyard.

Ms. Fahima, 32, is jobless and worried about her children’s future. She is still tormented by memories of nighttime telephone calls from police and intelligence agents. She does not know who killed her husband, but on the night he disappeared, she awoke from a nightmare: in her sleep, she had seen her husband crying, surrounded by security forces.

“Aminul used to work for the rights of factory workers,” she said. “I think that is why someone killed him.”