The only one in this mission you'll trigger next to the vending machine door right outside of Dr Kleiner's lab there is no cash just walk up to that spot and make sure it pops up the notification.
Once you jump onto the moving train, and then jump over to the other side of the tracks, you'll go into a boarded-up building. You'll see the icon on one of the walls and the cache is directly underneath it.
This one is impossible to miss once you get to the hole in the storage container that you have to crawl through, you'll have to break open this cache in order to proceed.
After getting through the first mounted machine gun area and proceeding to the tunnel opposite of it you'll turn to the left and jump over a red car to access this cache.
After you are shot at by a helicopter for the first time in the game, you'll need to go through a blue door to take cover. Under the grate floor you'll see the symbol marking this next cache.
Later on, while crossing this large pipe you'll see a lambda symbol off to the right. Break the planks and drop down to find this cache. I had to reload this one and grab it a second time to get it to actually trigger, so be sure to watch for the notification to pop up as you do it to make sure that it counts.
Once you get to a curved section of the sewer area there will be another section off to the left with a ladder. Up above there are planks that will lead you to this next cache.
Once you get to the area with radioactive waste you'll need to go to the left side and walk along the pipes over to the right to find the last cache on this level.
Shortly after starting this chapter you'll see a lambda symbol to your right. Climb up the ladder to find this cache.
Once you leave that tunnel you'll see a red barn straight ahead climb up inside all the way to the top, and dislodge the barrel to drop the crate containing the cache.
Pretty soon after this a gunship will drop off a few troops next to a circular grate with a lambda symbol. Inside of that pipe is another cache.
Once you start taking rocket fire from a couple of armored cars you'll need to go right up to the area underneath the second one. In here you'll see a hole off to the right side that you can get into, and then you can go grab the cache.
You'll see the lambda marking this cache as you're continuing through the area. Take out the bricks being used as a counterweight to lower the cache down and grab it.
Once you get to the part where the helicopter is dropping mines on you, you'll come across an opening on the left. Go inside there to find this lambda cache.
You'll eventually go through some half submerged pipe segments, and then into an opening with a lambda symbol up on the left side. Break the supports under that platform to drop the cache.
Further through you'll come to an area with slanted sides on the left. You'll see an opening with some green graffiti on the wall. Go up there to find the next cache.
Once you get up to a pair of bridges go to the left just before them. Up there is another cache in the dark area.
After you get the boat upgraded as you get to this fork in the water you'll need to take the right path, and back here there's a small shelter where the last cache for this level is.
There's only one lambda cache in this chapter. Near the beginning there will be a symbol marking a ladder you have to climb onto. When getting near it this one should trigger.
Shortly after meeting father Grigori, there will be a building with two large green generators climb up onto the left one, and there's an air duct with a cache inside.
Later on, you'll see two car traps. The further one is next to an area marked by a lambda symbol. You'll need to activate the trap, climb onto the car, and then jump behind the fence where the symbol is located to find this cache.
Shortly after that, you'll see father Grigory again before having to drop down into an alley. At the end you'll have to climb up a ladder and go across a wooden plank that leads to a hole in a tin roof. In here you'll find this next cache.
Much further into this chapter, after you get through the mines, you'll need to turn around and climb up these boxes. Right above the exit of the caves is the last cache for this chapter.
After the buggy is dropped down, you'll need to proceed up the hill. After you jump over the broken bridge, you'll go around the corner, and there will be a red shack with a lambda symbol on it. Inside of here, is the first cache for this chapter.
Near the first thumper there's a house with a cellar door to the right of it. Go into the seller to find this cache by stacking things to jump up into this room.
Later on after you defeat the gunship at NLO, you'll have to fight a second gunship. Once you get through this area you'll see a blue van which has another cache.
After passing a combine force field you'll see a fenced off area on the left with a large gas tank inside. Use a barrel to climb over the broken fence and the cache is inside of that area.
Shortly after the last one you'll see some large rock formations to your left, just before some buildings where drop ships are taking off of. By the left of that rock formation there's a small fenced in area where the last cache for this chapter is.
Proceed until you come up to a gate blocking your path. In order to open the gate, you'll have to use some batteries in a house to the right of this. Up on a ledge under the roof there's a combine rifle charge that you'll need to use your gravity gun to grab it to trigger this cache.
Once you get to the large sand area where you have to build bridges to move across, there's a metal building in the middle. You'll need to climb up onto the roof, and then up onto the ledge above it. This is where the other cache for this area is located.
Shortly into this chapter, you'll go into a room with three large pillars, and two sentry turrets above you. One of the double doors has a lambda symbol next to it, and a small hole which contains the first cache on this level.
After you come across a dead vortigaunt in a chair you'll need to go upstairs. You'll go past the laser trip wire and straight ahead is a door where you'll see a lambda symbol. Next to that you can slide the cell door open and grab the cache.
The last cache in this chapter is on the right side of the big laundry room. You'll go down a hallway and into a room where the cache is located as well as a poison zombie.
There was only one lambda cache in this chapter right after you and Alex split up. She'll open a gate for you and you'll see a vending machine on your left side. You'll need to use the gravity gun to pull the items down from on top of it to activate this cache.
The first cache in this chapter is right after you come outside after dropping down the elevator. You'll see two green dumpsters and a large blue one on your right. Stack boxes on the green dumpsters to get on top of the blue one and jump over to the ledge by the fence to find this cache.
After encountering hoppers you'll eventually get to an area where a combine soldier is shooting down from a window and below him is a small red shack with a lambda next to it. There's a small metal sheet here which you can move to reveal this cache.
After going through some buildings you'll get to an underground area with sentry turrets near a hole in the wall once you go through the hole the path will split go up the right side with stairs leading up to use your gravity gun to open the crates by the lambda symbol
You'll continue going through some underground areas and eventually you'll have to go around a large wall of rubble. Once past that turn around and you'll see a small shelter with a campfire. Here you'll find the next cache.
Later on a resistance fighter will drop a bridge for you to run across. Shortly after that you'll have to drop a bridge yourself. Right before that there's a lambda symbol on the wall and a cache below that.
As you go through a building with combine soldiers fighting zombies you'll eventually get to one of the lower levels where you'll see a lambda symbol through the doorway. Inside of this room you'll need to use your gravity gun to pull the cash items to you through a fence.
After defending Alex at the generator, you'll go underground, then you'll get to a room with combine soldiers above and zombies below down at the bottom. There's a small ledge next to a ladder where this next cache is located.
Eventually you'll come to an area in a sewer where there is a wall splitting two pathways. On one side there's a small hole in the wall marked with a lambda symbol. You'll need to use the gravity gun to pull the items from inside towards you.
Shortly after, and off to the left there's a passageway with pipe platforms to jump across leading towards a lambda symbol at the end with another cache.
The last cache in this chapter is after you go up the large lift. Keep fighting your way up and before you drop down to the platform that you exit from, you'll need to walk around the large red room, and back in the corner to see this cache.
The last lambda cache is pretty far into this chapter. After you fight a good amount of striders you'll go under an overpass. As you're moving through, a strider will break through behind you. You'll run into the opening to the left and continue through. Eventually, you'll go down a stairwell and hop through a hole to an adjacent building. The final cache is here.
As long as you triggered all of the other caches then you should now get the lambda locator achievement.
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