1. To the right of the waterfall there is a series of rocks that you can use to climb over. Switch to 'strength mode' and hop up.
2. Continue along the riverside. You have to move upriver.
3. You'll encounter several KPA patrols on your way upriver. Use the assault scope to take them out from a distance. Or, instead of engaging them, let them pass by while you stay hidden in cloak mode.
4. Once you get past the first wave of KPA, you'll hear KPA battling the alien at a distance. Once the alien gets away, move in and finish off the KPA.
5. Signs of the Alien's passing can be seen there. Including the torn up body of one of the archeologists. Yikes!
6. Another group of KPA is coming towards you. Use binocs to find them early.
7. Use grenades to take out groups of enemies.
8. When you reach the spot where your path crosses the river, watch out for this sniper on the other side.
9. Get to the other side of the river and continue. This area is crawling with KPA. The 'cloak mode' will be very useful here.
10. The flash bang grenades can be used to temporarily stun the enemy.
11. You'll find prophet waiting upriver. Approach him.
12. Enter the cave system with Prophet. End of chapter.