CHTAURA, Lebanon — The mountain range that forms a natural boundary between Syria and Lebanon has long served also as a wartime conduit for people who cannot travel legally — the gunrunners, the rebels, the dissidents and the ordinary citizens who just want to escape.

On one night last month, it became a death trap. A storm whipped up at the moment a group of about 70 Syrian refugees was climbing over the mountain to try to reach Lebanon.

In the darkness, wind and snow, they began to falter. The elderly fell behind. Children tripped. Men slipped. Unable to see their guide, the refugees became lost and scattered.

By daybreak, 15 people had frozen to death, a sad new milestone in the tragedy of Syria’s seven-year-old war. Refugees have drowned trying to reach Europe and are regularly shot on the Turkish border. But this was the first known instance of a group dying of cold, according to the United Nations refugee agency and Lebanese authorities.

It was also a reminder of the continued desperate efforts of Syrians to escape the fighting, even as the world closes its doors. The United States and Europe are not alone in restricting entry to Syrians — Syria’s neighbors also long ago shut their borders to refugees. For those still fleeing to Lebanon, which is hosting about a million Syrian refugees, the only way in is across one of the mountain smuggling routes.

The fate of these recent refugees first came to light after rescue workers posted photographs on Facebook, offering clues to the horrors of the night. A woman had died huddled in a thorn bush, the child she was carrying tipped upside down from her arms. And one little girl was found alive, lying in the snow. Someone took her to the hospital in the nearby town of Chtaura. Half of her face was burned away from frostbite, and she was comatose from the cold.

Among those on the mountain that night were Shihab al-Abed, 43, and members of his extended family, from the village of Barghouz in Deir al-Zour province. The village had been under Islamic State control for years but was too unimportant to be caught up in the battles that have killed more than 300,000 people elsewhere, and their lives had remained mostly peaceful, Shihab said, recounting the tale from his brother’s home in the Lebanese city of Tripoli.

Late last year, everything changed. The Islamic State was being driven out of all of its strongholds. More and more of its fighters began showing up in the village as they fled other areas. In November, the Syrian army overran a nearby town, and Barghouz suddenly found itself on the last front line of the Islamic State’s dwindling defenses.

After a night of intense fighting in late December, during which the family’s house was hit by a shell, they decided they would have to flee to survive, Shihab said. They piled into vehicles and made their way to Damascus, the Syrian capital — Shihab, his mother, wife, sister, four daughters and a son, three grandchildren, a sister-in-law, and two nieces.

Once in Damascus, they made contact with a smuggler who said he could take them to safety in Lebanon. The journey would cost $140 per person, and the route would be easy and short, the smuggler promised — just a half-hour walk, alongside the main road, and they would be in Lebanon. “But he was lying,” Shihab said.

When they arrived at the border on the evening of Jan. 18, instead of remaining alongside the road, the smuggler pointed the family up the nearby mountain, indicating a series of blinking lights high in the darkness that he said they were to follow. There they were met by another smuggler, their guide for the rest of the journey.

The path grew steeper, the weather worsened. The wind became a howling gale. The rain turned to snow. Like most of the refugees in the group, they were lightly dressed. Hanan, Shihab’s 13-year-old daughter, was wearing plastic sandals and kicked them off so that she could walk faster. It quickly became clear that the group was unable to keep up.

Shihab’s 70-year old mother, Hasba, was the first to fall back. Shihab’s wife, Anout, sister Dalal and daughters Amal and Abir stayed with her to try to help her along. Soon they had lost sight of the rest of the party. Then they lost Hasba. Amal was carrying her 1-year-old son, Yasser. Abir, seven months pregnant, was struggling too. She handed her year-old daughter, Beshayer, to another refugee.

The women grew colder and sleepier. “So we decided just to take a rest,” recalled Abir, who survived that night. “We lay down and said we would find the way in the morning.”

Up ahead, Shihab was carrying on, his niece Sarah, 3, in his arms. The rest of the night is a blur, he said. They ascended one mountain peak, descended and then another lay ahead. At one point, he fell and cracked his ribs. The girl in his arms had grown lifeless and cold. He could hardly walk. So he lay his niece down and continued. “I thought she had died,” he said.

When dawn broke, Abir awoke. Her grandmother, mother, sister and nephew lay immobile beside her. “They were stiff and frozen. I hoped they were just asleep,” she said. “I could see a house, so I went to get help. It turned out to be an army post. They went to fetch them.”

Seven hours after they had set off, Shihab and the other survivors reached the bottom of the mountain. He learned that, among the dead, were his wife, mother and grandson Yasser. His niece Sarah, her sister and her mother were unaccounted for.

At the hospital in Chtaura, civil defense rescuers were ferrying in others they had found on the mountain, some dead, some alive. Over the next two days they would find a total of 15 bodies.

Most of the survivors were treated and released, said George Kortas, a doctor and the head of the hospital. But one girl, estimated to be 3 years old, was in critical condition.

On the third day, she began to show signs of life. And on the fourth day, she spoke. “I want to go to mama,” she said in a weak little voice.

But no one came to claim the girl — until the fifth day, when her father showed up. Living in Tripoli, he had only discovered the fate of his missing family members when he saw the photos on Facebook. The woman found huddled in the thorn bush was his wife. The girl in her arms was his 4-year-old daughter, Heba. Only later did he learn there was an unclaimed girl in the hospital, his other child. It was an awkward reunion. He had only seen the child once, when she was an infant, because he was living in Lebanon while his family remained in Syria.

“She doesn’t know me, and I don’t know her,” he said. He cradled her as he fed her from a hospital tray.

Then she repeated the only words she had spoken. “I want to go to mama.”