Here’s how to do The Final Puzzle challenge in RE9 (Resident Evil 9: Requiem) in a clear, step‑by‑step way, plus what’s currently being discussed on forums and guides.

What The Final Puzzle Actually Is

The Final Puzzle is a hidden challenge that ties together a weird basement ritual, Marie’s Doll, the Severed Hand, and a specific code input in the Lead Researcher’s Office late in the game. You effectively need at least one mostly clean playthrough to set it up, then a second run or reload to actually trigger the challenge completion.

Phase 1 – First Playthrough (Get Marie’s Doll)

Your first goal is to “prepare” the world state and earn Marie’s Doll, which then carries over to later saves/new game.

1. Basement processing / blood grinder setup

  1. Reach the Care Center basement processing area (the room with the grinder and the pool of blood under the conveyor).
  1. Stand in the Processing Room and wait around 15 minutes while bodies drop into the pool. Many players wait 18–20 minutes to be safe.
  1. During the grinder encounter, do not kill zombies yourself; let them fall into the grinder if possible (you can stun them, but avoid final killing blows).
  1. Drop down into the blood pit when the sequence continues, then pull the lever to drain the blood before you move on.

Think of this as “priming” the puzzle: lots of bodies into the grinder + proper draining seems to flag a hidden condition.

2. The toilet step (the infamous “flush 8 times”)

  • After finishing the basement section, go to any bathroom and pick a toilet, then flush it exactly 8 times.
  • This matches the step often summarized as “flush a in the room eight” or “flush a toilet 8 times” in early datamined notes.

3. Get Marie’s Doll and finish the game

  1. Continue normally until the late evacuation / blood flood sequence in the Research Facility.
  1. After the huge blood machinery explodes and the area floods, look at the bottom of the staircase in that escape path; Marie’s Doll is lying on the floor or floating down.
  1. Pick up Marie’s Doll and finish the game with it in your inventory, or at least in your possession before the final stretch.

Once you’ve done this, the doll becomes available in your item box on future saves and playthroughs, which is crucial for the Final Puzzle.

Phase 2 – Second Run / Proper Save (Severed Hand & Clues)

For the actual Final Puzzle challenge to trigger, you need a save as Grace in the Care Center where you have the Severed Hand and access to the Blood Lab.

4. Start (or load) a new playthrough

  • Either:
    • Start New Game and rush back to the Care Center basement section, or
    • Load a save from before the meat grinder segment if you prepared one in advance (many guides recommend saving right after finishing the basement on the first run).

5. Get the Severed Hand again

  • During the Care Center basement/story path, progress until you reach the elevator section where the Severed Hand is found near it.
  • Pick up the Severed Hand; you’ll need it for the Blood Lab analyzer later.

6. Use the Blood Lab analyzer

  1. Go to the Blood Lab and use the Severed Hand on the analyzer/laser microscope.
  1. This reveals a code and starts tying letters to specific sci‑fi numbers (like U = 380,000 and C = 4.2 ly in related lore files), which are hints to the underlying logic of the final code.
  1. Strictly speaking, you don’t need to decode all lore hints to solve the puzzle, but doing so explains the “Let’s play”/“sweet pair” riddle.

7. Optional lore clues (if you care)

  • VIP Suite hourglass: Interact with the hourglass, unscrew it, let the sand fall, and see the U = 380,000 note.
  • Private Lab file (Ashcroft/Gracecroft Blood Analysis): Read it for C = 4.2 ly at the bottom.
  • Additional documents and the “Let the sweet pair hear the voice” line help explain that the letters map to symbolic sun/moon/star patterns for the final lock code.

You can skip a lot of this if you just want the raw answer; the puzzle still works.

Phase 3 – Bringing It All Together (Doll + Emily + Code)

Now you’re back in the Care Center with Grace, you’ve got the Severed Hand, and you must ensure Marie’s Doll is available.

8. Retrieve Marie’s Doll from the item box

  • Load the Grace save in the Care Center after all the previous conditions are met (you’ve completed a run and collected the doll).
  • Go to an item box and withdraw Marie’s Doll.

You should now have in your inventory:

  • Marie’s Doll
  • The Severed Hand (already used at the Blood Lab)
  • Emily (the child/figure you carry in this segment)

9. Visit the Blood Lab again

  • Carry Emily through the blood and interact with the Severed Hand in the Blood Lab one more time.
  • This step is often described as “carry Emily to the blood in the lab to the Severed Hand again,” and it seems to flag the save as “ready” for the final box interaction.

Final Step – The Puzzle Box Code (Exact Solution)

With Emily, Marie’s Doll, and the Severed Hand conditions satisfied, head to the Lead Researcher/Leader’s Office where you previously used corrosive and found quartz.

  • Approach the puzzle box / lock in that office while holding Emily and with Marie’s Doll in your inventory.
  • Input the final symbol sequence that the community has confirmed as the working solution:

Sun Sun Star | Sun Moon Star | Sun Moon Sun | Moon Star Moon

Once you confirm this pattern, the Final Puzzle challenge pops as completed and you get the expected reaction/reward tied to the “Let the sweet pair hear the voice” riddle.

Mini FAQ & Forum Talk (Quick Scoop Style)

Is it possible in one playthrough?

  • Technically, yes—if you know every step in advance and route your saves correctly—but almost all guides treat it as “first run: get Marie’s Doll, second run: solve the puzzle.”
  • Most players find it less frustrating to do it over two runs so you don’t soft‑lock yourself by missing a step.

Why all the weird conditions?

  • The “wait 15 minutes with bodies falling,” “don’t kill zombies,” and “flush a toilet 8 times” conditions are all part of the meta‑ARG‑style design, similar to the finger puzzle in RE7.
  • Community datamining and big streamers (Hazeblade, Bawkbasoup, others) helped lock in the exact conditions around March 1–3, 2026; it’s been a trending forum topic since.

What if it doesn’t trigger?

  • Double‑check:
    • You waited long enough in the Processing Room and drained the blood correctly on your first run.
* You flushed exactly 8 times.
* You actually picked up Marie’s Doll and then finished the game at least once.
* On the Grace save, you re‑used the Severed Hand in the Blood Lab while carrying Emily before entering the code.

If any of those are missing, you may need to redo part of the sequence or, in the worst case, another run—painful, but that’s part of why the challenge is considered so “final.”

SEO‑Style Meta Description

Learn how to do the final puzzle challenge in RE9 (Resident Evil 9: Requiem) with a full step‑by‑step guide, including Marie’s Doll, the Severed Hand, basement grinder conditions, and the exact final lock code, plus the latest forum discussion and community discoveries from early 2026.

Information gathered from public forums or data available on the internet and portrayed here.