Terrified, Saroo woke, trapped on a train hurtling hundreds of miles away from his home in Khandwa, India. There was nothing the 5-year-old could do besides yell the name of his older brother: "Guddu!"

Because Saroo and Guddu's mother worked from sunrise to sunset carrying hot bricks and the money she made hardly fed her four children, the two brothers had been searching for loose change and food scraps at a train station in a nearby village when Saroo had boarded a train, looking for his brother. Sleep-weary, Saroo dozed off, expecting to wake up to his brother's face.

But when he woke up, he was alone.

"It (getting on the train) was just an impulse decision that, in fact, changed my destiny for life," Saroo told NPR.

Lost

When the train finally stopped, Saroo stepped off and was overwhelmed by the crowd of people who engulfed him, speaking a foreign language and uninterested in helping a little beggar boy. He was in Calcutta, 930 miles away from a home no one understood the name of.

After weeks of escaping kidnappers, begging on the streets and dodging bullies, Saroo was given sanctuary in an orphanage. Because he only knew his mother as "Amma" ("mommy" in Hindu) and because the name of his small village wasn't known this far away, Saroo had little hope of ever returning.

So the orphanage sent him even further from his home. They told him about Australia, a place he had never heard of, and about Sue and John Brierley, his new parents. Saroo told Vanity Fair that he remembered thinking, "Here's a new opportunity. Am I willing to accept it or not? And I said to myself, I'll accept this, and I'll accept them as my new family."

And he did. He went to school. He learned English. He made a new home.

But his past still burned in his memory. In his mind, he could still see the mud brick walls of his tiny Indian home, the waterfall he played in and the faces of his mother and brother who surely longed to know he was safe. But how would he ever find them again?

The search begins

Nearly two decades later, Saroo had graduated from college and the desire to reconnect with his roots came back stronger than ever. In his book, Saroo said, "The past was never far from my mind. At night, memories would flash by and I'd have trouble calming myself so I could sleep." He opened Google Earth to look at pictures of India.

Then he realized - the waterfall, the tower, the train station, the paths to his little home - these images still vividly reverberated in his memory. If he could just find matching images on Google Earth, he would find his home.

His search quickly became obsessive. Knowing he must live about a night's journey from Calcutta, Saroo relied on information supplied from Indian friends about train speeds in the 1980s and on tools he learned in an applied mathematics class he'd taken in college to create an algorithm to narrow down his search area.

Even so, his search often seemed fruitless, driving him to abandon it, only to return weeks later, staying up until three or four in the morning, following train lines, virtually flying over India in search of the images in his mind.

Six years after he began his search, Saroo's search landed on a bridge. He had seen that bridge before. It was at the station where he was separated from his brother. This was it. Saroo kept searching the map until he discovered more and more: the the fence where he'd scarred his leg, a water tower, the dirt paths that led to his home.

He returns to India

After months of seeing India through his computer, Saroo was again staring down at the green of Indian landscape but this time, it was through the window of an airplane. He stepped off the plane and into the land that had haunted him for 25 years.

By memory, Saroo was able to weave through the streets to his home. Standing in front of it, the mud-brick house seemed impossibly small and in that way, it was different from what he remembered, altered by memory and by his new life.

However, the woman who came to the door was not his mother. In bits of English and broken Hindi, Saroo gestured toward a childhood picture of himself, saying the names of his mother and brothers and sister. The woman recognized none of it. In broken English, she said, "These people don't live here."

Neighbors began to gather, curious about this stranger in their village. Finally, a man took the picture Saroo held in his hand, "Come with me," he said, "I will take you to your mother."

The homecoming

His mother looked different, older and weathered, but it was still her. Since that day on the train, Saroo had known seeing his mother's face again was impossible and yet, there he was, seeing her again.

Watch this inspiring story in the acclaimed film "Lion" starring Dev Patel and Nicole Kidman.