Resident Evil 4/Chapter 4-2

Mine entrance
You are now in an underground room below the laboratory. Get the Green Herb near the elevator and go down some steps to find the Merchant and a typewriter. Get three barrels and Handgun Ammo here. Also pick up "Luis Memo 2"; it's by Luis and details how Salazar revived Las Plagas from fossilized remains and that more remains are sought in excavation so that more Ganados can be created.

The third venue for target practice is here. When you're done, go on to the next area.

Plagas mine
There is a tunnel leading to an excavation site where villagers are trying to dig up Plagas spores. Start down the passage to find a small group of villagers. Get a Velvet Blue from a mine cart and two barrels.

A trolley track starts here; check next to it for a clue about tripping a circuit breaker. Keep going to the end of the track to find a number of villagers working the excavation. Fight as many as you can from the track since it's a defensive position, then drop down and finish clearing the area. At least one of the villagers has dynamite. There are two villagers you can't reach because the path is blocked.

Check for items. Also check the center of the area to see what is being mined, fossilized parasites. These would be dangerous if your body wasn't already riddled with parasite larvae.
 * Shotgun Shells below the side of the track.
 * Velvet Blue from a cart next to where the track is broken further on
 * 2800 PTAS from crates near the southern ledge
 * 5000 PTAS behind the circuit breaker on the southern ledge

Operate the lever next to the far end of the track to release a trolley; it will jump over the gap and stop at the end. This trips the circuit breaker though. A villager or two will be alerted by this so clear the room again. Go to the southern ledge to reset the circuit breaker; a larger group of villagers appears including Dr. Salvador.

When these are gone, return to the lever and pull it again to lower the mine cart the rest of the way, then grab the dynamite inside. This isn't to be used as a weapon, but to clear the boulder that's blocking the path ahead. Place the Dynamite in the cavity and back off a bit to watch the explosion. Dispose of the remaining villagers and get two barrels near the exit, then go through the door.

Lava pit
This room has a metal grate floor over a pool of lava. There is a suspicious looking trap door in the middle of the floor. Locate the lever to operate it near where you came in; you press the action button once to grab the handle and look at the door, and press it again to open the door. You may want to practice this once, then go back to the previous area and come back in to reset it.

Cross the room to the door on the other side and two El Gigantes (two Los Gigantes?, Dos Gigantes?) come through it. Dodge the giants and climb the ladder to the top of the narrow platform on the far side of the room. Then, before or as they start to shake the platform, jump to the zip line glide down to the lever that operates the trap door. Grab the lever and watch to see if one of the giants steps onto the door and if so, pull the lever. Hopefully the giant will fall into the lava and cut down the odds a bit for you. If this doesn’t work because the giant wasn’t in the right spot you can try again after a minute or so. If you do sink one of the giants, stay clear of the hole for a while since he might grab you when he’s in the lava and drag you down with him. It might be possible to get both giants on the trap door at the same time, but they don't exactly have a herd instinct.

This trick will only work once since the since the machine locks itself after dropping a giant, but you can still use the zip line in your battle with the second one to get some distance from him. So fight the remaining giant as your previous encounter with this type of monster. Incendiary grenades do nothing here, apparently this giant is pretty used to fire already, but flash grenades still make a good distraction. It's a good idea to conserve Shotgun Shells here since you may need them for the next level. The giant drops 15000 PTAS.

You can, if you want, just fight both giants and get an additional 15000 PTAS. In this case keep using the zip line to keep away from them and concentrate your attacks on one of them until he's defeated. It's debatable whether this is worthwhile since if you sold the extra ammo you'd use you could bet a good part of 15000. If you take damage and have to buy a First Aid Spray as result then you've actually lost PTAS in the deal. Certainly don't attempt it if you're low on ammo.

Check the room for items. Continue to the next room, get two barrels and go on to the next area.
 * First Aid Spay
 * Flash Grenade
 * Shotgun Shells

Cavern
This is a huge cavern filled with the flying insects you first encountered at the dome. Equip your shotgun and approach the mouth of the cave, but don’t go too far out, when you’ve attracted the attention of some insects go back to the cave to fight them there. The idea is to use the narrow cave as a choke point, both to group them together and for keep them from attacking from the side or above. Keep blasting until the first wave dies down and try to lure more into the cave if you can.

Go out and check the pedestal for a clue about two lights. Actually what you need to do is pretty obvious without it and the clue is more cryptic than helpful. Explore the area watching out for hidden groups of insects. There is a ramp on the right leading up to ledges and bridges forming a loop around the upper level. Collect items as you go.
 * Green Herb next to the pedestal
 * Flash Grenade at the bottom of the ramp
 * Shotgun Shells at the top of the ramp
 * Green Herb in a small cave to the west
 * Red Herb on the south ledge near the exit
 * Green Herb in a small cave to the east
 * Handgun Ammo near the entrance to this cave
 * TMP Ammo on the northeast ledge above the pedestal

Go into one of the small caves an activate the switch there. This turns on a light next to the exit door and triggers another insect attack. Make a stand behind the narrowest point in the cave and defeat them. Now do the same in the second small cave.

The two lights are reflected off a mirror and onto the exit door, melting it and opening the way out. A few more bugs will hover around near the exit. When you get close they attack so defeat them. Press the switch to open the gate.

You enter a tunnel where you have to time your way past columns that will crush you if you get trapped underneath. Just run under the first column, then go under the second column and quickly jump down. Press the lever here to lock one of the columns ahead into place. Run under a third column and stop under the locked one, then run under the last one.

Get the Royal Insignia from the pedestal in the room at the end. Attach this and the Crown Jewel to the Crown to make the Salazar Family Crown which is now ready to sell.

Check the pedestal again and it will raise you to the surface.