Arrival at Zion

Arrival at Zion is a main quest in the Fallout: New Vegas add-on, Honest Hearts.

Quick walkthrough

 * Follow Jed Masterson
 * (Optional) Defeat the White Legs assault.
 * Move into Zion Valley.
 * Travel to the Dead Horses Camp at Eastern Virgin.
 * Speak with Joshua Graham.

Detailed walkthrough
Once you appear in Zion after completing Happy Trails Expedition, follow Jed Masterson along the canyon path. A group of White Legs will attack, killing the group. You must kill all of the White Legs to continue the quest, but there is no way to save any of the caravan members (their deaths are scripted). The White Legs may come equipped with powerful weaponry, including anti-materiel rifles, 12.7mm submachine guns, riot shotguns and brush guns at higher levels.

Cross the bridge to meet a Dead Horse scout named Follows-Chalk and have him join as a companion. As you make your way towards Joshua Graham, Follows-Chalk will warn you to stay along the path. You will soon meet a giant yao guai but it will not attack ("Must have been all full of gecko", as Follows-Chalk notes). Be warned: subsequent yao guai will attack you.

Further along, Follows-Chalk will note a cliff with a view. If you climb the cliff to the top, you will trigger Follows-Chalk's companion perk, Well-Stacked Cairns, for temporary +3 Perception and some additional map markers added to your Pip-Boy's map. Continue to follow the map marker to Eastern Virgin and the camp of the Dead Horses.

After a brief conversation with a Dead Horse Disciple of Canaan, Joshua Graham can be found deep inside Angel Cave. Meeting him completes the quest.

Bugs

 * One of the White Legs might become invincible if you leave the ambush without defeating them, thus making it impossible to complete the optional part of this quest.
 * When reaching the area where the yao guai attacks, the game will crash every time, making it impossible to go further.
 * When the yao guai attacks, it is completely invisible. The audio files are still played, and Follows-Chalk made his normal comment, but the yao guai could not be seen, including after being killed.
 * Some White Legs may be non-hostile and too far away from the cliff to kill them, making the optional part of the quest impossible to complete.