The Final Puzzle (Tips + Troubleshooting)

Most of the guides on the Internet contain unnecessary steps in order to solve the Final Puzzle.
This guide was made keeping that fact in mind, with some tips and clarifications added to make the solution look more simple.

It's worth noting that this puzzle has trigger mechanic. Meaning that the game has a counter of how many steps were properly completed in order to solve the puzzle.
This mechanic shows after flushing the blood during the 1st step in Care Center's Basement. More info is provided at the corresponding moments of this guide.

My personal reccomendation is to do this puzzle on your first or second playthrough. DO NOT do this on Insanity or a separate playthrough, because it is pretty much pointless.

https://steamcommunity.com/sharedfiles/filedetails/?id=3681157302
NOTE: Items DO NOT transfer to the save files of your first walkthrough. You have to do the next step on a separate walkthrough.

Instead, do it either on your first playthrough if you are playing with guides, or do it on your 2nd playthrough by choosing Casual diffciulty. You can complete all of the remaining achievements (except those tied to Insanity difficulty) on this exact playthrough, if you're fast enough, that is.

So, on this playthrough to clear all the remaining achievements:

• You must not use any heals (Steroids don't go in count) [Casual difficulty heals the player over time].
  
• You must not use the Blood Collector as Grace.
  
• You must complete the game under 4 hours.

The puzzle will add around 20 minutes to the total time counter. Make sure you are doing everything fast, and you'll end up ending the game just in time.

I, personally, finished the playthrough in 3:51:32. Here's the screenshot (not in English, soz).

While playing as Grace, you'll end up in the basement of the Care Center.
Proceed to the Processing Room's part across the Joint Plug. DO NOT turn the vessel just yet.

• Make a save file #1

This exact save is going to come in handy if you for some reason will end up not getting the 4 hour mark for the Speed Demon achievement. That way, you'll skip the first 1.5 hours of your gameplay on a retry.

The very first step that you have to do — is to wait for 15-20 minutes for 115 zombies to fall into the bloody water. Black body bags DO NOT count towards the... counter.

You must not hit the pause button or anything that stops the course of things going in-game. Stand still, you might wanna go AFK for this bit. Place a timer for your own convenience if you wish.

• Make a save file #2

Once the time has come — make a second save file in a separate slot and turn the vessel. Go down, the grinder will start working.
Now the very important detail is to let all the zombies to go into the grinder. You MUST NOT kill anyone here.
The tip is to stand as far to the grinder as possible and shoot the enemy's legs in order to stun them. The other tip is NOT to use the melee attack, since it can potentially push Grace herself into the grinder.
Do not worry about standing exactly at the place where the zombies come out. They won't bite. They are busy standing up.

NOTE: There MUST NOT be any alive zombies left on the conveyor.



Once done — take the joint plug, go back and go through the vents. You'll end up in a pool of blood. Flow it out, and now the game must either say that "A ton of blood flowed out" or that "A torrent of blood flowed out"



=Torrent of Blood screenshot=

The reason? The aforementioned trigger mechanic
If you already completed one the upcoming steps (flushing the toilet) — this means that you activated 3 triggers, hence the game saying the phrase "A torent of blood"
If you haven't yet completed one the upcoming steps (flushing the toilet) — this means that you activated 2 triggers, hence the game saying the phrase "A ton of blood"

If it says "A lot of blood flowed out" — something went wrong, reload the save and try again. Wait for more zombies to go for the blood bath, or make sure you didn't kill anyone.

Go back to the Guard's Office and sit Emily on the couch.
Now we have to go to the Restroom. We need to flush any of the toilets at least 8 times.

NOTE: All of the flushes summarize, so you can, for example, flush 2 at once 4 times, and it'll count as 8.



NOTE: This step can be completed before the Step 1.

• Make a save-file #3

Now, back to the Guard's Office and make a third save file. We'll need Emily on our last step of the puzzle.

After the previous step, proceed with your playthrough.
Once you escape the Research Facility, enter the 2nd room of Collection & Testing, which goes after Emergency Evacuation Route

Now, beside the ladder there should be the Marie's Doll laying around. If it's not there — something went wrong on the previous steps. Reload the save files and make sure you did everything correclty and properly.



After you got the doll — put it in the Storage Box.

From now on, all you have to do is finish the game.
After that, the Marie's Doll will carry over to all of your other save files

NOTE: Marie's Doll DOES NOT transfer to the save files of your first walkthrough. You have to do the next step on a separate walkthrough.

Now, after completing the game, go back to the Save File #3.
Take Emily with you, get the Marie's Doll in your inventory and go back to the Lead Researcher's office. The Puzzle Box where you first got the Sun Quartz will become interactable once again.



You gotta enter the soluiton. It goes as follows:

Sun-Sun-Star-Sun-Moon-Star-Sun-Moon-Sun-Moon-Star-Moon
or if you prefer it that way:
1-1-3-1-2-3-1-2-1-2-3-2

Clarification:
- Star
- Sun
- Moon

After that you'll hear the laughter and you'll get the notification that the puzzle is solved. That's it!

Marked as unnecessary due to the fact that the hand is only needed to get hints regarding the final cypher.

NOTE: If the Marie's Doll didn't appear or something went wrong during the puzzle — try to roll back to the Save File #3 and analyze the hand according to the next step.

After escaping the basement on the lift, turn around and collect the Severed hand. This item is crucial for this puzzle.



NOTE: Severed Hand DOES NOT carry over.
(not that you'll need it after getting the Marie's Doll)

The hand is not needed for the solution. It was needed for a hint do decypher the puzzle, but since the final code is already known there's no need to take the hand with you.

Now we gotta analyze the Severed Hand. Take it to the any analyzer of the Care Center.
The solution to the analyzer puzzle is provided on the screenshots.

• Make a save-file #3

Now, back to the Guard's Office and make a third save file. You can put the Severed Hand in the Storage Box. We'll need Emily on our last step of the puzzle.

Q: Do I have to keep Mary's Doll in my inventory for the whole time?
A: No, you can drop both the Severed Hand and Mary's Doll into the Storage Box.

Q: I always get the wording "A lot of blood..." instead of "A ton of blood..."
A: Not enough zombies fell into the blood or you killed somebody on the grinder or someone didn't end up in the grinder. Repeat that part.

Q: I didn't get the Severed Hand!
A: I got it on my very first playthrough without following the Final Puzzle guide. Make sure you didn't stash it away, worst case scenario — do the previous steps once again

Q: The Marie's Doll is not there for me!
A: Check your storage box again. If it's not there — something went wrong during the previous steps. Try to repeat them one by one, start off by flushing the toilet.

Q: I didn't get my 20.000 points!
A: Enter the Challenges menu.

Q: I solved the puzzle but didn't get my reward!
A: Try to do some unnecessary steps like collecting the hand and taking it to the analyzer, or to collect blood for example.

- Add more troubleshooting info (check for many possible outcomes and the need of certain requirements).

11.03.2026
- Additional information regarding the "A torrent of blood flowed out" phrase was added.
Credits to the user SkyNet for pointing that out.

13.03.2026
- The hand steps were marked as unnecessary.
- Additional information regarding the need of all zombies ending up in the grinder was added.
Credits to the user NemesisXploder for pointing that out.

14.03.2026
- Some corrections made to the Overview.
Credits to the user Hello Kitty for pointing that out.

17.03.2026
- The information that items DO NOT transfer to the save files of one's first walkthrough was added.
Credits to the user Baster for pointing that out.
- The correction that the blood flow is only a trigger-check and is not important towards solving the puzzle was added.
- There is a theory that the player sometimes has to do some specific steps in order to get the reward for solving the puzzle.

19.03.2026
- The information that any toilet flush does the trick was added, along with the information that the flushes summarize.
Credits to the user MavcskuOG for pointing that out.
- The information that analyzing the Severed hand helps in case the puzzle is not solving even after going through all the steps properly was added. NOTE: There is an assumption that it is actually a bug, since the sound effect is played and the puzzle is solved, but the challenge itself doesn't check out.
Credits to the user whatevrr for pointing that out.

21.03.2026
- Clarification was made that there should be AT LEAST 8 flushes.
Credits to the user Eric Draven for pointing that out.