For refugees and migrants trying to reach northern Europe, the journey is fraught with risks. Families can become separated and reuniting them can seem like an almost impossible task, as John Sweeney found out when he met a Syrian woman in Hungary, desperate to find her son.

The sorrow written on the face of the old lady sitting by the train window set her apart.

Fakhria told me her story haltingly and in small, confusing packets so I only fully comprehended the danger she faced when she collapsed at Hungary's border with Austria and, I feared, could have been dying. But I am getting ahead of the story.

I was travelling though Hungary, having followed the 1,300 mile (2,100km) route people take from the Greek island of Kos to Central Europe.

"In all honesty I regret making this journey," said Fakhria. "If I knew it was going to be like this, I wouldn't have come."

Fakhria was in her early 60s, I guessed, dressed in a black headscarf and simple frock. She didn't have a bag or any belongings with her. She told me she was from Kobane, the Syrian town turned to rubble in the battle between IS and Kurdish fighters backed by American air power.

Image copyright Getty Images Image caption Much of Kobane is now in ruins

This summer, her whole family decided to leave and seek sanctuary with relatives in Denmark. Fakhria started the journey with her son, Mahmoud, and her brother and his family.

Their route took them through Hungary, but they heard a false rumour that if the Hungarians stamped their passports, they could only end up in Germany and go nowhere else.

Fearing a Hungarian stamp would thwart their goal of Denmark, the family slipped into the country and walked through woods for six hours in the middle of the night.

How could they send my children away while I was in the hospital? Fakhria, Syrian woman

"I was in so much pain. I was beyond tired, exhausted," said Fakhria. "At the end of it all, the police captured us and held us. Then I said to myself, 'Staying in my country would have been better than coming here.'

"The rain was pouring down. The son of my youngest son, he was crying and inconsolable. We told them, 'We need a doctor, the child is sick.' They told us, 'Wait, the doctor is coming now', but the child was almost dying in our arms."

Fakhria and her family were taken to a camp surrounded by barbed wire and, for a time, had to stand out in the rain: "I felt like I was in prison. Did I come to Europe to just to go through all this sorrow and pain?"

At the camp, she felt sick. As aid workers took her away for treatment, she gave her purse with all her money to her son, forgetting it also contained her medicine. "They took me to the hospital for what should have been a 30 minute visit. I wanted them to take me back but they made me stay the night and when I got back to the camp I couldn't find my children. They had gone. I just kept on looking for them but I couldn't find them. How could they send my children away while I was in the hospital?"

Image copyright Getty Images

Fakhria was then taken from the camp to Budapest railway station. She was alone. "I don't speak a word of English. I don't have one penny to my name."

As she told me about her isolation, tears streamed down her face: "The pain is excruciating. My heart has been wrenched. I'll never forget it. I spent two days at the station crying, trying to locate my children, to no avail. I was asking every random person I could. No-one could translate. They couldn't understand me, not even the basic details of my situation. The only word I knew how to say was 'family, family'."

I spent a few hours in the station myself, watching the Hungarian police move thousands of people from the ticket hall in the basement to the platforms and found the process exhausting and dehumanising. To be on your own in that place with no money and no means of contacting your family would be hell within a hell.

"I was going to and fro, searching, asking, but everyone was in their own world," said Fakhria. "I was thinking, 'I'm searching for my children and asking about them, someone will help me,' but no. They looked at me as if I was nothing. They had no thought of me. They were in their own world. Each moment I felt like I was dying over and over again."

By chance, she bumped into her nephew Mustapha and his family. They took her under their wing and together they traipsed towards Austria.

But Fakhria desperately needed to find her son. She reminded me of my grandmother and I wanted to help. "Listen to me," I said. "We will help you find him. It won't be easy but we will find him. I promise you. We will use Twitter and email and Facebook and Snapchat."

Media playback is unsupported on your device Media caption The video we posted on social media

The train came to a stop shortly afterwards, still inside Hungary, two miles short of the border with Austria. Everyone was made to get off the train and walk, Fakhria included.

At Hungary's frontier point Fakhria collapsed, her eyes fluttering, then closing, her skin going a horrible shade of grey. And then, finally, we realised she was diabetic. Medics from the Hungarian Red Cross rubbed a dextrose tablet on her lips and she came around and soon she was on her feet and struggling the final steps into Austria.

We put a video on the BBC News Facebook page, which was viewed more than 320,000 times.

At the same time we heard that her son Mahmoud had used an Austrian website, Trains of Hope, to call out for his mum.

So it was, that in Vienna station, Fakhria and her son were reunited - a bright spark of hope that I shall never forget.

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Watch Panorama - The Long Road: Europe's Border Crisis, on BBC One at 22:35 on Wednesday 30 September.

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