Resident Evil 4/Chapter 3-2

Observation Hall
The radio transmission you get from Salazar will give you a hint of what's to come. After the transmission, turn around and head through the door.

Prison Area
Break the barrels for items, go around the corner, and drop down. Walk along the corridor until you get to the corner. Equip the rifle, and aim down the next corridor. The mist is actually breath from a new enemy known as a Novistador. Shoot the area where the breath originates to kill the creature in one shot. Now you can move down the corridor safely. Ignore the hole in the wall to the right, and be sure to pick up the item the creature drops; it's a new treasure known as a Novistador Eye, and it comes in three colors, Red, Green, and Blue. Move into the next area and snipe the two bugs waiting in the water below. Drop into the pool and collect the items there, then climb the ladder on the other side. Open the next door, and watch out for the Novistador that drops down from the skylight. Use your shotgun to deal with it. Once the first one is dead, another will attack from the left. Deal with it, collect the Eyes they drop, and walk down the corridor to the left.

Another bug is waiting on the right, so blast it with the shotgun before it can attack. Head back to the central area and search each cell for items and a document. Investigate the area full of water, then head back down the corridor, move through the destroyed cells, and enter the room at the end. Break the crates here and open the red chest to find a Butterfly Lamp, a treasure that you can combine with Novistador Eyes of three different colors to increase its value. Turn the red valve to drain the water. Open the door, but don't move forward. A Novistador is hanging from the ceiling ahead. Snipe it, then move forward and snipe the one waiting in the destroyed cells.

When you get back to the central area, another Novistador will attack from a cell across from you. Deal with it, then head back to the corridor where you killed the first Novistador. Head back to the hole in the wall, where another Novistador has appeared at the end of the small passage inside. Snipe it, collect its Eye, and break the crate here. Return to the central area and drop into the lower area. Another Novistador will drop in behind you. Run up the stairs to narrow its path of approach, and blast it with the shotgun when it's close. Grab the Velvet Blue from the drain, and break the barrels at the top of the stairs for items. In the next area, move between the swinging blades as they pass in front of you, and jump the gap ahead using the same timing. Grab the Velvet Blue, then climb the ladder, smash the barrels here, and exit through the door.

Observation Hall

 * 1) When you regain control of Leon, head through the door to the right. Grab the ammo from the barrels near by, then drop down the ladder. Head down the hallway, and you'll hear something run then jump, but you won't be attacked yet. Head forward until you reach the hallway facing south, then stop. Take out the rifle, and aim toward the south end of the hallway.
 * 2) You'll see drool hanging from the air that marks one of the invisible acid-spewing bugs down here. Luckily, they're as susceptible to headshots as anything else in this game, so take it down with the rifle by aiming just above the visible drool. All the insects drop "Eye" gems, which you'll be able to combine with some other treasure later. Head slowly down the hallway, and keep an eye out for the drool of the insects.
 * 3) If one gets close to you, blast it away with the Shotgun, but otherwise try to snipe them wherever you can. Past the first one, there'll be a pool of water to the right, with two of them near the far ladder. You should be able to snipe both of them, so once they're dead hop down, and collect their eyes, the Handgun Ammo to the left, the Velvet Blue in the water, and the TMP rounds in the pipe, then climb up.
 * 4) Head through the door, and another one will be waiting for you in the hole in the ceiling. Another will come at you from down the hallway, which you probably won't get the opportunity to snipe. Check the cells to find some Handgun Ammo, a Yellow Herb, some Shotgun Shells, and a memo from Luis. Before you check the cells to the east, though, head around the hallway to the east to take out another bug; if you do him first, you should be able to snipe him. Follow the path through the cells to find a room with a wheel you can turn, and some boxes with Shotgun Shells and a Green Herb. In the treasure chest is a Butterfly Lamp, which you can combine with the Eyes you pick up from the bugs.
 * 5) Use the wheel to drain the water, then head back out to the main area. Be wary, because the bugs will have respawned now. There's two waiting for you in the hole in the ceiling just outside the room, and one in the main room, which'll come out of the one cell you couldn't open before, and one more which will drop at you from the ceiling.
 * 6) Hop down into the water, and kick down the gate. Yet another bug will drop down behind you when you do, so run into the next room, turn around and blast it. Grab the Velvet Blue in the corner, then head up the stairs. Continue on into the next area, and you'll see a bunch of pendulums swinging back and forth across the path. Just wait for them to pass as you go by them to avoid being chopped up.
 * 7) Grab the Velvet Blue on the other side of the blades, then head through the door. Climb the ladder, get the loot from the barrels, and head through the door. You'll stumble in on a little meeting of Ganados. If you've got any Grenades, toss one right in the middle of the group to take a bunch of them out at once. Hop across the first chandelier to the other side, then use the second one to head to the other section. Flip the switch here to open up all the grates, then finish off the red robed Ganado to get an Illuminados Pendant. In the northeast corner of the upstairs is an Elegant Mask, so make sure to grab it.
 * 8) If you don't kill them, they'll eventually spot you and head into the next area, and you'll lose all the loot you could have gotten. Save, then head up, sell the loot to the Merchant, and head through the door next to him.
 * 9) Head forward, and grab the Red Herb on the table, then head up the stairs to find a note from Salazar. Go through the green door to find a bunch of Ganados waiting to ambush you. These ones aren't quite so willing to chase you through the door, so first use the Rifle to take out the crossbow guys, then take out the ones wandering around the room. Grab the loot from the urns, then head through the door to the southwest.
 * 10) Once inside, grab the loot from the urns and head up the stairs to find another Ganado, then head through the door. Around the corner is some Rifle Ammo, so grab it then head around the catwalk. You'll be able to drop down here and engage the last couple Ganados, but when you do the red one will run away. Kill the two there, then give chase, making sure to grab the Shotgun Shells and Pesetas in the room he flees through.
 * 11) Through the green door in the corner, there'll be a shield Ganado to slow you down. Take him out and keep following the red guy. When you get to the door at the bottom, you'll find he's brought out a Gatling gun to attack you. Whatever you do here, don't give him a clear shot. Retreat back to the doorway to the catwalk, which'll give you enough cover to avoid his attack and let you snipe him. Once he's dead, go down and collect the Gallery Key.
 * 12) Head back to where the red Ganado was first standing, and use the key to get through the door. Shoot the deer's eye to get a Velvet Blue, then break the urns to get some Shotgun Shells. Go to the console in the middle of the room to start the puzzle.
 * 13) The objective here is to make it so six people are displayed in the four pictures. Switch 1 turns the two pictures on the left; Switch 2 turns all but the rightmost picture; Switch 3 turns all but the leftmost picture; and Switch 4 turns only the two pictures on the right. Hit the switches in this order: 1,4,3,2. Hit Ok, then head through the now open door.
 * 14) You'll get another cutscene with Salazar, and then be attacked by more Ganados. Take them out, and if you need some cover head to the door directly to your right and use it as a bottleneck. You'll find a Yellow Herb at the top of the stairs here as well. As you fight them off, more crossbow wielders will come out, and eventually a pair with rocket launchers will fire at you from behind the painting, but mercifully only once.
 * 15) Clear out the room, then hit the red button on the wall in the alcove to the west. Now, head toward the small room in the south, and another pair of Ganados will launch rockets at you; just get behind cover, and continue to the room. Hit the button there, hidden under the urn, to extend the bridge. When you go back through the door, you'll find another pair of rocket launchers pointed at you, so just retreat through the door and let it take the blast, then take out the rocket launching ones (who'll die in one hit), and the three scythe-wielders who join them.
 * 16) Once that's all done with, grab the Goat Ornament from the chest, then head out through the door to the west. Save here, then head down the hallway. Grab the Handgun Ammo from the urn there, then head through the door to the west. Shoot the Spinel down from the wall, and continue on.
 * 17) Head down the walkway, and shoots the crows on the fountain to get some loot. There's a small room off to the side here that contains the Broken Butterfly, but you won't be able to get it until you get Ashley back later.

Salazar's Garden

 * 1) Take a left, and follow the path. Through a gate, you'll see a kennel with three wolves in it, some of which might mutate. Blast them all and collect whatever loot they drop. From here, head to the east and follow the path until you get to a treasure chest. A pair of wolves will come at you, so put them down, then head back to the west.
 * 2) Take the third right to find a Yellow Herb, then the second right. Head north until you reach an opening, take out the wolf here, then go south on the path to the right to find a treasure chest with a Red Gem. Now, head back out and go west, then up the stairs. From the fountain, grab the right half of the Moonstone.
 * 3) Head back down the stairs, and continue your sweep clockwise around the maze, taking out the dogs as you go. There's a First Aid spray in one alcove in the northwest corner, and a Spinel in the northern one. Once you've collected them, head back to the southeast corner and cross the walkway to reach the northeast corner, and grab the left half of the Moonstone from the fountain. Head back toward the door you passed which you needed the Moonstone for, and watch out for dogs.
 * 4) Combine the two halves, then use them on the door to open it up, and enjoy the cutscene that ends Chapter 3-2.