Locate the White Legs leader, Salt-Upon-Wounds, and deal with him.
Return to Daniel at the Narrows.
Following the completion of this quest, all named characters will leave Zion Canyon, but generic tribals will remain.
Though he is a companion, the player cannot talk to Joshua, or trade gear with him while he is in your party. He will simply decline with a variety of terse responses such as 'Now is not the time' or 'He he. I don't think so'.
Once you start this quest, until finished, all the enemies other than the White Legs disappear from Zion Canyon.
Once the quest has begun, fast travel is unavailable until completion.
It is not possible to save all the Dead Horses and Sorrows, due to some of their deaths being scripted.
PCPlayStation 3Xbox 360 If Joshua is too far behind the player when rock detonation occurs, you may be notified that he has left your party and lost his perk, but he will not initiate the dialogue telling you to look for another way around, and when you reach Salt-Upon-Wounds, Joshua will not be there, and you will be unable to move or interact.you can solve this by waiting for Joshua before you enter the area and kill him, it will fail the mission but will activate a new one and you can fast travel and get the map to get out of Zion (you will NOT get any or the items at the end but you will keep your save) or reload a save before Joshua leaves your party.