The details (briefly) go thus: the citizens felt that the eldest Kuru-son should become now the King as the present King was old and blind. Duryodhan went mad with jealousy and the old resentment against the Pandavs all came back. He then requested his father to send the Pandavs and Kunti to Varnavat on some pretext. Dhritarashtra was not easily persuaded but his son convinced him anyway. In a few days, when the festival of Pashupati was about to be celebrated in Varnavat, the Pandavs and Kunti wished to attend it. Dhristarashtra saw this as an opportunity and spoke a lot about the festival and the delights of the city, in order to make them go. Meanwhile, Duryodhan and his brothers and friends start to win over the people's hearts by being very generous with the state's treasure.
When the Pandavs actually go to Varnavat, Duryodhan, unbeknownst to his father, already has a house of lac and other inflammable materials built there.
Vidur warns the Pandavs with riddles before they go and Yudhishthir being intelligent, finds the hidden meaning of his words and suspects great danger, so the brothers spend their days in Varnavat cautiously. Vidur later sends a helper to dig a tunnel under the house for them to get away. After the tunnel is finished, Bhim (2nd Pandav) sets fire to the house and gets out by the tunnel. Vidur makes sure that the architect, the tribal woman and her sons who built the house of lac die in the fire, so that the news of the Pandav's death will spread everywhere and they will have some peace before they decide to come back home.
The details of the story are available in Mahabharata Book 1, Adi Parva, Jatugriha Parva,
Mahabharat Book 1 - > Jatugriha Parva. I am sure I have not got all the great details, but you can read the story in this chapter.