A unit that makes a failed charge moves directly towards its target a number of inches equal to the highest dice rolled for the charge.
A unit that makes a failed charge has started towards the enemy, but soon realises that it is impossible to cover the distance. The warriors in the unit lose impetus as the enthusiasm for the charge peters out.
If a unit makes a failed charge it moves directly towards the target a distance equal to the highest score rolled on the 2D6 of the charge roll (i.e. if the dice showed 2 and 5, the failed charge move would be 5"), wheeling around impassable terrain and units, both friends and enemies, by the shortest route.