Khandwa Railway Station, India, from where Saroo and his brother Guddu began their ill-fated journey. Credit:Raj Patidar He and Guddu cycled to the station and boarded a train for nearby Burhanpur. There his brother asked him to wait on the platform. ''I was very tired,'' Saroo recalls. ''My brother … always came back. I decided, 'I'll just go to sleep and when he comes back he'll wake me up'.'' Saroo never saw his brother again. He woke after midnight to a deserted platform. ''I saw this train in front of me, and I thought, 'I'll get on board because I think my brother's on it'.'' He boarded the train, thinking it would take him home, and found a seat where he could lie down. But the train was going in the opposite direction. Through the night and next day, the train swept all the way across the country, a small boy asleep in a third-class carriage.

Fatima Bi, Saroo's mother at her home in Ganesh Talai in the city of Khandwa. Credit:Raj Patidar From the plains villages of Madhya Pradesh, the train carried Saroo due east to India's former capital, Calcutta, a grimy industrial city of more than 10 million people. Saroo could not even name the place from where he'd come. He could barely ask for help. He spoke Hindi. The people here spoke Bengali. ''I was absolutely scared. I didn't know the city I was from, I didn't even know how to count to five, I didn't know left from right.'' Saroo Brierley in Hobart. Credit:Richard Williams Calcutta, then and now, is a hard city. Its main railway station, Howrah, is ceaselessly overcrowded and overwhelming, indifferent to a lone, terrified child.

''For a person not even a metre in height to go into a place like that is extremely scary. No mother would let her child go into a place like that.'' Saroo could not read the platform signs. None of the names being blared out across the public address system sounded familiar. And no one had time for one more hungry kid on the platform. For days he caught train after train, hoping one would take him home. ''I tried so many trains but they were all dead ends. I tried to talk to people … [but] there was the language breakdown. Nobody wanted to help. Everyone had their own things to do, their own family. I was just another kid …wanting money or food.'' After a week of riding trains to distant, unfamiliar cities, of sleeping curled up in the darkened corners of platforms and of begging for food, Saroo gave up trying to get home. ''Life instinct kicked in … I thought about going home, but that was a dead end. I knew that I had lost it.''

Outside in the city of Calcutta, Saroo tried swimming in the Ganges. Twice he was pulled in by its currents and had to be rescued. Once he fled from a man who had offered him food and shelter, but who held him too close. He survived as best he could. ''When it came to food, you just had to beg … Sometimes you had to steal things. Whatever got you through the night, you had to do.'' After months on the streets of Calcutta, Saroo wound up, one among thousands, in a government detention centre for lost children. Unable to tell anyone even the most basic information about himself, he was sent to a foundling home, and put up for adoption. Within weeks, he was told he was going to live in Australia. Packed onto a Qantas plane, and given his first bar of chocolate - ''the whole block melted in my hand because I didn't know what to do'' - Saroo flew alone halfway across the world.

He began a new life in Hobart with his adoptive parents, the Brierleys. In most respects, his was a typically Australian, outdoorsy childhood. Tasmania's climate was unfamiliar, but he soon adapted. His English flourished, and he spent summers sailing sabots, and diving for crayfish and abalone. He went to suburban schools, and studied in Canberra, where he earned a Bachelor of Business, before returning to Tasmania to work for his family's engineering business. Today, he is Australian in all things: in manner and speech and outlook, as well as in citizenship. But he never forgot India. ''I was determined to keep all those memories I had. For some reason, I believed that I would need them at one time. All those things [that happened] when I was little kept the streets alive in my head for such a long time.'' In Canberra he met students from India, and began asking them if they had heard of the train station he called Bharanpur (actually spelt Burhanpur). No one could help him.

India, famously, runs on its railways. Every town, regardless of significance, has a train station that connects it to the massive, labyrinthine network that pulls a disparate country together. Finding his home, Saroo concedes, ''was like finding a needle in a haystack''. So he narrowed it down. Estimating that he had ridden that train for about 17 hours, covering somewhere around 80 kilometres an hour, Saroo calculated that his home town was around 1400 kilometres from Calcutta. He turned to Google Earth. ''For four years I searched, looking up and down, [then] I started looking from [Calcutta] train station and following the railroad back. But there were so many rail tracks it was sending me absolutely crazy.'' Finally, he found it, 1484 kilometres from Calcutta: Khandwa. He looked closer. He saw the dam he used to swim in as a child, a bridge he remembered, too. ''That's where I was born.'' He found a Facebook group called My Hometown is Khandwa, and posted a string of questions to confirm the town was his: ''Is there a fountain in the CBD?'' ''Is there a theatre nearby?''

All of the answers came back in the affirmative. In 1987, a few weeks after her sons, Guddu and Saroo had gone missing, Fatima Bi was told a boy's body had been found near the tracks at Burhanpur station. It was Guddu. His death has never been explained. The police were never greatly exercised. Deaths of poor children, by accident or intent, are too common in India. There was no sign of her other son. Through 26 long years of waiting, Fatima lived her life. She worked as hard as her body would allow. Her other children grew up, married and had children of their own. But she never gave up hope that Saroo would, one day, return.

''I prayed every day, all of my life, and my only prayer was that God would fulfil my wish to hold my son again before I die,'' she tells The Saturday Age,in the half-light by her front door. ''I never lost faith.'' For all the tumult of Saroo's life, Fatima's existence has changed little in the quarter-century since her son left. She has moved house, but has stayed in the same neighbourhood. She lives alone now in a low-slung terrace, a rickety camp bed in the corner of the single room, a hotplate on the floor in a corner. Too old to cart bricks, she works still, six days a week, as a cleaner in a house in the city. For years, any money she saved, she would spend travelling, following rumours and hunches, looking for her son. ''I had one wish in my life,'' she says. ''And that was to see my son again.'' ARMED only with the mind-map burnt into his brain at five years old, Saroo arrived back in Khandwa last month, seeking to retrace his last steps in the city.

''It was different. The old houses and construction had started to fall down, new construction had been built on top, but I unmasked it. I kept walking and I thought, 'I'm here'. I stood at the little town centre … I just stood and gazed.'' He walked on, through the foreign but familiar streets, until he found himself facing the front door he had left as a child a quarter of a century ago. No one was home, but word of Saroo's arrival spread in the tight-knit Muslim neighbourhood of Ganesh Talai, and an envoy was dispatched. Fatima was being brought to Saroo at the same time as he to her. As he rounded the corner into her narrow street, she saw him, and she knew. ''I recognised him immediately. He was my son. I recognised him from the mark on his forehead [where a horse had kicked him when he was very young], and he has the same chin as his brothers.''

Holding her hands to her chest she describes holding her son again after so many years. ''I embraced my son without losing any time,'' she says, in tears at the memory. ''I had so much joy. The happiness in my heart was as deep as the sea, I experienced heaven on this earth when my son met me.'' From a Hobart cafe, Saroo recounts the same moment. ''She had aged, but you could still see the structure of her face that remained in my memory. The simple stuff that makes us who we are.''

Saroo stayed for 10 days in Khandwa, visiting his mother and being reunited with his sister Shakila, eldest brother Kallu, cousins and his childhood friends. He intends to return, perhaps annually. Fatima lives the life now of a contented woman. She carries with her pictures of Saroo and she has his mobile phone number saved in her own. Her English is limited, like Saroo's Hindi, but she just likes to hear his voice. ''His life is in Australia now, they are his family there. I say to them, 'Thank you so much for the new life you have given him'. But I hope he will stay connected with his roots,'' she says.

''For me, I am happy. He has come home.''