Vidura sends a miner to meet Yudhishthira. The miner tells him of a plan to build a tunnel from the palace to the river Ganga. As Purochana is always with them, they go hunting to wean him away from the palace to enable the miner to do his work. After about a year the tunnel is ready and the door hidden by covering it with a costly rug. Just in time, as the miner tells Yudhisthira of the plan to set fire to the palace on the fourteenth day of the dark fortnight.
(Human history is full of stories where the poorer are victims of such chicanery! Truly some are more equal than others?)