Chapter 4-1 is the ninth level of Resident Evil 5.
After battling the mutated Irving, Chris and Sheva regroup aboard Captain Josh Stone's boat taken to a cave reported by the dying Irving. Chris and Sheva go into the cave alone as Captain Stone withdraws. (You can get a lot of treasures in this chapter. It provides the most gold in the game.)
Before heading out stock up on ammo in the nearby hut. During this level you will encounter many spider-like creatures Bui Kichwa they are very easily defeated, use a flash grenade to kill them instantly. They only have a single attack which is latching on to you. After dispatching the first one in the beginning on the cave continue on. Continue into the cave and you will see a ladder, keep following the path and do not go up the ladder and continue on and turn left and climb up into the alcove finding a chest open it and you find a Topaz Triliant. Go back and climb up the ladder. There will be more in the pathway. Continue on and you will see a torch smash it with you knife and you will get another gem. Deeper into the cave there will be more bui kichwa dispatched with ease. As you continue to descent you will find more smashable items to obtain gems. Enter the double doors and you will initiate a cutscene.
Go left and jump down, follow the path and you will find more items. You will initiate another cutscene after you arrive at the bridge. The Nydipaya tribesmen will try and crush you making a column fall destroying the bridge. This will reveal a new path, jump down and you will have to face multiple enemies. After dispatching the enemies fight your way up the stairs and you will soon regroup with Sheva. After making you way up and regrouping there will be a chest filled with items. Follow the path again until you see another stone chest open it and it will reveal a trap door initiating a dodge sequence be quick to land that will save and conserve your health. You'll find yourself in the middle of a cross-shaped area. Explore the place and you will come across three treasure chests but guarded by the bui kichwa and the tribesman. After defeating the enemies a door will open itself and yet you face more enemies which are easily taken out with a rifle. After dispatching the enemies you'll find yourself in a rather big room with a lot of vases in it. By walking towards the other end of the room, you'll trigger a cutscene. Go to the centre of as you will have to turn a wheel opening a door and releasing a trap consisting of balls of fire. Be quick as the door will quickly close. (You may also shoot those balls, but that may take too long, so better just avoid them).
Enter the door and you will initiate another (quite long) interactive cutscene where you're running down a hallway. Tap the buttons (Note it's not only running but jumping as well), but at the third jump remember to press the left and right trigger buttons to not fall down.
After this pull the chain and it will make a massive stairway leading downwards appear. Follow the flights of stairs and keep going forward and you will come across a statue with a pair of chains. Sheva will that the first one and you will have to take the second one. Repeat this process of pulling the statue's chains and note that you will have to face some of the Nydipaya tribesmen. Note that as every statue goes into the rock after the chains have been pulled, there will be a treasure lying in front of them. Smash any pots and you can find a grenade launcher equipped with flame rounds after going down the stairway making two lefts, in a silver case. The forth one actually consists of two statues, one on the ground floor and one on the upper level, just above. In the 'room' adjacent to the lower one you should find a mine in one of the vases. Finally the fifth statue will be the last one. The fifth one will lead to a cutscene of an armoured Popokarimu which can be defeated with explosives and you will get a soul gem for it but an alternative way is to run up the flight of stairs initiating an interactive cutscene this time tap the button rapidly and you will crush the Popokarimu.
The easiest way to kill the Popokarimu is to place a mine in some distance to the last statue, about in the middle of the 'room' (before pulling the chains). It will walk over it before even attacking you once, and by now your weapons should be strong enough to kill it the first time it's stunned by the mine.
After defeating the Popokarimu and entering the door you will initiate the final cutscene. Wesker will be injected with a serum provided by Excella Gionne after her departure. Wesker will have a flashback, the encounter with Spencer and his brutal killing.