The blurry image of her son flickered on her smartphone screen. The 3-year-old was squirming on his father's lap.
"Where's Momma?" the father asked him.
"There is no Momma," the boy replied.
The video call in the summer of 2016 was the last contact that Dr. Indira Karakayeva has had with her son. In April 2015, her estranged husband, Temirlan Amangeldiev, kidnapped the boy and left Russia with him to join the militant group Islamic State in Syria.
He told her that he was in Raqqah, the Syrian city that the group had claimed as its capital, and that their son was never coming home. Then he hung up.
Roughly 4,000 Russian Muslims — many from the North Caucasus republic of Dagestan, where the family lived — are believed to have left their country to fight for Islamic State. Russian authorities believe that hundreds brought their children.
Now, as Islamic State is on the verge of losing its last substantial territory in Syria and Iraq to a U.S.-led coalition and the Russia-backed Syrian military, hundreds of Russians like Karakayeva are looking for as many as 1,000 children who have been orphaned or abandoned.
"Indira's story, unfortunately, is pretty typical of what we are seeing," said Marina Yezhova, the government advocate for children in Dagestan and the head of a national committee formed last month to repatriate the orphans.
Yezhova said that there are as many as 600 registered inquiries into missing children who had been taken by their parents to Iraq and Syria, but that hundreds more families are probably not coming forward because of shame or fear that Russian security forces will crack down on them for associating with terrorists.
As Russian media attention intensified, the Kremlin set up a 24-hour hotline last month to assist families searching for their children. In the first week, it received 480 calls.
"A lot of these guys went over there and married once, sometimes twice or more," Yezhova said. "There's more children out there than what we've seen on the television."
In fact, hundreds of children are believed to have been born in Islamic State-occupied territories, in addition to those who were taken there by their parents, and most of them have no documents. Identifying relatives is a painstaking process that involves multiple government agencies, cross-border coordination and DNA testing.
In Dagestan, the tradition is that men steal their brides.
Amangeldiev was 24 when he kidnapped Karakayeva in the summer of 2012 and kept her in his parents' house. She was a 20-year-old medical student. After her parents reluctantly granted permission, the couple married in a civil ceremony.
The pair moved to Astrakhan, near the Caspian Sea, where Karakayeva continued her studies. Within four months, she was pregnant.
Amangeldiev frequently visited Moscow for construction jobs, and it was there that Karakayeva believes he fell in with a crowd of devotees to Wahhabism, a strict form of Islam, and was recruited into Islamic State.
He began insisting that the family live by strict Islamic law, ordering Karakayeva to cover herself in conservative clothing and limit her activities outside the home. He would beat her when she resisted, even when she was pregnant.
After their son was born April 18, 2013, Karakayeva wanted to give him a traditional Dagestani name. But Amangeldiev insisted on the Arabic name shared by the first Muslim caliph and the current leader of Islamic State: Abu Bakr.
Four months later, Amangeldiev broke his wife's nose. She took the baby and moved back to Dagestan to stay with her parents. She returned to Astrakhan several months later to finish medical school and told Amangeldiev to stay out of their apartment.
She tried on two occasions to get full legal custody of Abu Bakr but failed, despite telling judges that Amangeldiev was a radical Wahhabi and a terrorist.
"They just weren't listening," Karakayeva said.
With visitation rights, Amangeldiev showed up at her parents' house unannounced on April 5, 2015, to pick up his son, who was staying there while Karakayeva was at school in Astrakhan. Her grandmother, who was baby-sitting, reluctantly gave in to the father's angry demands and handed over the boy.
In phone calls with Karakayeva, he promised to bring the child back in an hour. Then two hours. Then the next day.
Two days later, he sent Karakayeva a message on WhatsApp. He was in Turkey and on his way to Syria to make Abu Bakr a "lion" for Islamic State. "I'm going to defend Muslims from the nonbelievers," he wrote. "If I die, I'll go to heaven. You will die in hell."
After Amangeldiev stopped calling and changed his telephone numbers and social media accounts, Karakayeva tried to track him down. His few associates whom she knew were radical Wahhabis, many of whom had also left Russia to join Islamic State. Finally, she found a couple whose daughter had enlisted in the group and had been in touch from Syria.
In response to her parents' inquiries, the woman sent a photograph in July of this year that she said had been taken in Raqqah more than two years earlier. Two children were sitting together. One was the woman's daughter. The other was Abu Bakr.
Based on information from the family, Karakayeva has come to believe that her son was being raised in Raqqah alongside the children and wives of other fighters from Russia and neighboring countries, and that Amangeldiev married a woman from Kazakhstan and had a daughter with her.
"Amangeldiev isn't particularly smart. He's a guy who would easily follow others," Karakayeva said. "But he knows how to survive, and he's using his son as a shield. He's probably respected by those terrorists because he's giving away our son to be the next generation of Islamic State."
In August, Russian television aired a report about dozens of Russian-speaking children found in a Baghdad orphanage. The children described horrific stories of losing their parents to bombs and gunfire in Mosul and other Iraqi cities once held by Islamic State.
The story caught the attention of Chechen President Ramzan Kadyrov, whose republic in Russia also saw large numbers of citizens join Islamic State.
In recent years, Kadyrov has cast himself as the defender of Russia's 14 million Muslims, who make up about 10% of the country's population, and has forged close ties with leaders in Saudi Arabia, Jordan and Syria.
Karakayeva, whose letters asking Russian President Vladimir Putin and other officials for help had gone unanswered, saw the Chechen president's attention to the children's plight as a breakthrough in her search.
She sent him a message on Instagram, where he posts daily, and pleaded for help. He never replied.
In September, she took a bus from the North Caucasus city of Stavropol, where she works as a doctor, to Grozny, the capital of Chechnya, in hopes of presenting her case to him.
For two days, she waited outside Chechnya's commission for children's rights. She was told Kadyrov was too busy to meet with her. Disheartened, she gave authorities dozens of documents about her son's case and boarded a bus back to Stavropol.
"I was just scared before, but now I have nothing left to lose," she said. "I'm willing to try anything to get him back."
The last information Karakayeva gathered about her son is that a woman from Azerbaijan had taken him to the Syrian city of Dair Alzour, where they were hiding in a basement to take cover from airstrikes.
She said she is convinced that when Islamic State is defeated, her boy will be found. She wanted his face on the internet, so that if he's located someone can identify him and bring him home.
She scanned through her smartphone to the last photograph she had of them together. She was smiling, and their cheeks were pressed together. Abu Bakr was just over a year old.
To read the article in Spanish, click here
Ayres is a special correspondent.