He went missing at the age of 5. Orphaned at six. 25 years later, Saroo Brierly set out to retrace his journey.

The BBC has the beginnings....

'Saroo was only five years old when he got lost. He was travelling with his older brother, working as a sweeper on India's trains ... That fateful nap would determine the rest of his life...he fell asleep and had a shock when he woke up 14 hours later. Though he did not realise it at first, he had arrived in Calcutta, India's third biggest city and notorious for its slums.'

After begging on the streets of Calcutta for a year, Saroo was adopted by an Australian couple. Raised there, his adoptive parents encouraged him to rediscover his roots.

CNET reports - it started with a search of Google Earth.

'With vivid memories of -- but not the name -- of the town he was born, he started searching the Internet for clues. Brierley multiplied the 14 hours he knew he had been on the train by the average speed of trains in India to determine how far he traveled that night. He then drew a circle around Calcutta and determined that Khandwa was the town he was looking for.'

When he discovered the waterfall where he used to play, he then jumped on social networking services. Australia's The Mercury reports...

'He then joined a Facebook group for his home town Ganesh Talai and managed to piece together .