But his life was upended in March 2015, when he left for a pilgrimage to Mecca. His wife was supposed to take the children to visit her parents in Orlando, he said. But when she stopped responding to his texts, he began to worry.

After days of silence, he reached her parents, who said she and the children were gone, but refused to say more, he said. So he contacted the F.B.I. and returned to Florida, learning that his wife, their children, then 4 and 10 months old, and his wife’s sister, had flown to Turkey to cross into Syria to join the Islamic State.

A few weeks later, he received a call from Syria while he was driving on the freeway, he said. A man with a British accent asked him whether he was the father of Yusuf and Zahra. Mr. Shikder said yes and asked where they were.

“In the Islamic State,” he said the man told him.

He gave Mr. Shikder one month to join them in Syria or said his wife and children would be taken away from him.

About a week later, his wife called and told him how she, her sister, and their children had been smuggled into Syria and had their passports taken away, he said. That was the start of an intermittent and painful correspondence between him, his wife, her sister and other members of the Islamic State.

Sometimes his wife sent him videos of his children playing and put them on the phone, he said. But he never knew whether they were in danger.

Image A family photo of Mr.Shikder’s children, Yusuf, a boy, and Zahra, a girl. Yusuf is now now 8 and Zahra 4.





“Many times I was very worried because I was seeing fighting, I was seeing airstrikes, I was seeing Assad’s soldiers,” he said, referring to Syria’s president, Bashar al-Assad. “I was seeing people being killed.”