Once upon a time there was a great warrior, Prince Rama, who had a beautiful wife named Sita.
There was also a terrible demon king, Ravana. He had twenty arms and ten heads, and was feared throughout the land. He wanted to make Sita his wife, and one day he kidnapped her and took her away in his chariot. Clever Sita left a trail of her jewellery for Rama to follow.
Rama followed the trail of glittering jewellery until he met the monkey king, Hanuman, who became his friend and agreed to help find Sita. Messages were sent to all the monkeys in the world, and through them to all the bears, who set out to find Sita.
After a very long search, Hanuman found Sita imprisoned on an island. Rama's army of monkeys and bears couldn't reach the island, so they began to build a bridge. Soon all the animals of the world, large and small, came to help. When the bridge was built, they rushed across it and fought a mighty battle.
When Rama killed the evil Ravana with a magic arrow, the whole world rejoiced. Rama and Sita began their long journey back to their land, and everybody lit oil lamps to guide them on their way and welcome them back.
Ever since, people light lamps at Diwali to remember that light triumphs over dark and good triumphs over evil.