What did the other two plan while he was gone in The Pardoner's Tale.

After discovering the eight bushels of gold coins, the drunkards realized that they could not carry the gold home without people seeing them and thinking them thieves. The youngest suggested, they should draw lots, and one of them should run back to the town to fetch bread and wine, while the other two protected the treasure. Then, at night, they could agree where to take the treasure and carry it safety. As soon as the youngest had gone to town, however, the two remaining drunkards plotted amongst themselves to stab him upon his return, and then split the gold between them. While he was in the town, the youngest thought of the beauty of the gold coins, and decided to buy some poison in order to kill the other two, keeping the gold for himself. Thus, he went to an apothecary, bought some “strong and violent” poison, poured it into two of three wine bottles (the third was for him to drink from), topped them up with wine, and returned to his fellows.