Climb Ev'ry Mountain is a quest given by Captain Gilles from Bitter Springs. A sniper has been attacking Bitter Springs, kiiling NCR soldiers and civilians. It is related to No, Not Much, with the target holding the key to the supply crates, and when you ask for more information from Gilles.
The sniper is located in a cave west of Bitter Springs. To reach the cave, you will have to approach it from the south west. It is a steep slope to the cave entrance, requiring a combination of jumping, and searching for the next ledge.
When you reach the cave, you will speak with Oscar Velasco. He will immediatly attack if you are wearing NCR armor, or are with Boone. He will describe his story about Bitter Springs, about how his family was killed. If you have a speech skill of at least 50, you may convince him to head to Red Rock Canyon and return to the Khans, or to charge Camp McCarren. If you mention to him that the Captain wants to resolve the situation peacefully, you need at least a speech of 25 to leave safely.
To complete the quest, either convince Oscar to stop attacking Bitter Springs, or kill him. Return to Gilles to complete the quest; she states that she prefers a peaceful resolution, to avoid any more bad blood from being spilled.