(Optional): Speak to Dancing Flame at the northernmost map marker (the one closest to the riverside). The Courier has several options when speaking to him.
Tell him and his Dead Horses to back up and stay put so that they don't get killed, while the player character goes to "smash White Legs alone." He will be a little upset, but will say that since the Courier is a friend to the Sorrows he will stay put, but that they had better kill the White Legs.
With a 75 Speech check, the Courier can convince him to leave by saying that he's no match for the hardened White Legs warriors. He and his companion will depart, saying that "angry ghosts" will have to be enough for the Sorrows. This will end the quest, but the White Legs remain at the burial ground.
The Courier can say "sure, whatever," and let the two Sorrows tribals fight. This will make the fight easier, as the two warriors will keep one or two of the White Legs preoccupied. Dancing Flame and his companion will survive the fight if one is quick about taking the White Legs out. With Joshua Graham in the party, this should not be a problem. If Dancing Flame or his companions die, the quest is failed.
They can also be told to wait and not do anything "crazy." Dancing Flame will then wait, but not forever. If the Courier proceeds to wipe out the White Legs, Dancing Flame and his companion will have left. This ends the quest.
Optional: Talk to the Sorrows at the burial ground.
Kill the White Legs desecrating the Sorrows' burial ground.
This quest is only available if Flight from Zion is active, otherwise the location will be empty, apart from any other creatures that spawn nearby.
There is a lean-to and a couple of containers just below the raised area which the burial mounds are on. These are present only between the beginning of this quest and the end of Flight from Zion. Anything stored in the containers, and not retrieved before the end of Flight from Zion, will be lost.