The mission is an optional stealth mission. This means if Tyler is discovered, the stealth is lost, but the mission can continue. Stay crouched and low, and head to the first campfire. Waste the enemy there and proceed into the mine tunnel. There will be at least four enemies you have to neutralize inside.Take out the next two enemies in the mines (quickly) and follow the HUD marker as best you can; you should encounter a second campfire with an enemy nearby -- kill him and move towards the mine's exit. A final (fourth) enemy will be at the mouth of the mine cave.