During this side mission, William requests that the player brings him some Yarrow. Upon delivery, William tastes the Yarrow, claiming it to have medicinal qualities; he then gives the player a crafted remedy as a reward.
Following the mission, William can later be found other times as a random encounter in the wilderness, where he will request the player to collect more plants in exchange for other tonics. After a few encounters he tells the player that he is leaving and that they may never cross paths again and bids farewell.
Despite saying this, William can actually still be found across the five states as a random encounter, but may still say the same thing.
- Tall Trees, West Elizabeth - near Tanner's Reach
- Lonnie's Shack, Scarlett Meadows, Lemoyne
- Cholla Springs, New Austin - between Armadillo and Ridgewood Farm
- Grizzlies West, Ambarino - Northwest of the Mysterious Hill Home.
- Grizzlies West, Ambarino - Top of the Chelonian camp hill, northwest of Moonstone Pond. (Possibly only after or during We Loved Once and True III)
- Great Plains, West Elizabeth - East of Manzanita Post and south of Beecher’s Hope.
- Roanoke Ridge, New Hanover - Mossy Flats
- Scarlett Meadows, Lemoyne - West of Ringneck Creek and east of Old Greenbank Mill
- The first encounter with William is the only one that's marked on the map, and his only guaranteed location, as every subsequent meeting with him is a random encounter.
- The player will lose honor if they steal William's horse.
- Despite saying that he is traveling far away, William can still be found once again across the five states.