The Mermaid Mask Demo Walkthrough: Full Puzzle Solutions & Investigation Guide - Guide

The Mermaid Mask Demo Walkthrough: Full Puzzle Solutions & Investigation Guide

Master The Mermaid Mask demo with our step-by-step walkthrough. Solve the serpent cabinet puzzle, find every clue in the Illusion Theater, and uncover Mortuga's fate.

2026-07-18
The Mermaid Mask Wiki Team
Quick Guide
  • The Mermaid Mask demo walkthrough covers the initial investigation at the Stone Top Inn and the Mortuga Submarine.
  • Key Mechanic: Use the map button in the bottom left to navigate between Silkworm-on-Sea locations.
  • Critical Puzzle: The Mess Hall serpent cabinet requires matching geometric shapes to the number of sides.
  • Main Objective: Investigate the locked-room murder of Captain Magnus Mortuga in the Illusion Theater.
  • Essential Tip: Examine every item in your inventory, including the back of posters and the contents of medicine bottles.

Arrival at the Stone Top Inn

The demo for The Mermaid Mask begins at 4:00 AM in the Stone Top Inn, located in the eerie town of Silkworm-on-Sea. As Detective Grimoire, you are accompanied by your partner Sally. The atmosphere is established through environmental storytelling, starting with the items left on the bar.

Video Highlights:

  • Initial exploration of the Stone Top Inn and character introductions.
  • Reviewing the case file for the murder of Captain Magnus Mortuga.
  • First look at the town map and the mysterious green light.

Before leaving the inn, you must interact with several key objects that provide lore and context for the upcoming investigation.

Item NameTypeDescription
The HelmsmanNovelA nautical fantasy adventure by J.D. Wearman belonging to Sally.
Case FileDocumentDetails the murder of Captain Mortuga in a locked room.
PhotographEvidenceImages of the crime scene and the victim, Magnus Mortuga.
LetterDocumentA handwritten note from Captain Seafoam hiring the detective.
Pro Tip

Open The Helmsman novel in your inventory to read the first chapter. It provides thematic parallels to the "terrible thing waiting in the depths" that you will encounter later.

Navigating Silkworm-on-Sea

Upon leaving the inn, you are introduced to the map navigation system. The town of Silkworm-on-Sea is bathed in an eerie green light emanating from the harbor. While the demo limits exploration, several points of interest establish the town's history.

Town Square

  • Central Hub: Connects the Inn to the Harbor.
  • Atmosphere: Deserted and foggy with strange lighting.
  • Key Visual: The source of the green light in the water.

Abandoned Buildings

  • Mr. Grimp Emporium: A currently empty shop.
  • Fortuna Hall: An old theater billboard for Waylon Wolf.
  • Lighthouse: Restricted access located high on the rocks.

The Harbor

  • Main Objective: Where the Mortuga submarine is docked.
  • Interaction: Board the submarine to begin the formal investigation.
  • Visual Clue: A glowing "wooden boy" figurehead on the deck.
Observation Required

Check the submarine's name on the hull. It was originally named "Seafell" before being crossed out and renamed "Mortuga," suggesting a history of mutiny or hostile takeover.

Boarding the Mortuga Submarine

Once you board the submarine, the green light begins to fade, suggesting the vessel itself (or something within it) was the lure. The interior is dark, requiring you to find a light source immediately.

1

Restore Power

Descend the ladder into the pitch-black entry room. Locate the lever on the wall to activate the pink-tinted emergency lights.

2

Check the Control Room

Attempt to enter the control room. It is locked from the inside, but a note from Captain Seafoam is taped to the glass.

3

Follow Directions

The note directs you to the crime scene: one floor down at the very back of the submarine.

4

Investigate the Mess Hall

Before heading to the crime scene, stop in the Mess Hall to gather essential items and solve the first major puzzle.

Submarine LevelKey RoomsNotable Features
Upper DeckForedeck, EntranceWooden boy figurehead, light lever.
Middle DeckMess Hall, KitchenSerpent statue, sun tablets, cooking pans.
Lower DeckIllusion TheaterCrime scene, stone cauldron, blood trail.
Environmental Lore

The pink light in the submarine is created by burning a specific substance. While not critical for the demo, this detail hints at the unique technology used by the Mortuga crew.

The Serpent Cabinet Puzzle

In the Mess Hall, you will find a large metal statue of a serpent with a built-in cabinet. This cabinet is locked by four rotating dials, each featuring different geometric shapes. This is a primary hurdle in The Mermaid Mask demo walkthrough.

Puzzle Logic: The number of sides on each shape must correspond to the numbers visible in the surrounding environment or the internal logic of the dial sequence.

Dial PositionRequired ShapeNumber of Sides
LeftTriangle3 Sides
TopSquare4 Sides
RightHeptagon7 Sides
BottomNonagon9 Sides

Once solved, the cabinet opens to reveal a bottle of Sun Tablets. These tablets come in three varieties, which may serve as a comparison point for evidence found later at the crime scene.

Mess Hall Completion Goals:

  • Solve the serpent cabinet dial puzzle
  • Collect the bottle of Sun Tablets
  • Inspect the puffer fish lamp
  • Observe the Z-shaped (or S-shaped) table arrangement
Item Discovery

The Sun Tablets are a brown glass bottle containing three varieties of medicine. Keep these in your inventory to compare against the "Moon Vial" found in the theater.

The Illusion Theater Investigation

The climax of the demo takes place in the Illusion Theater. This is where Magnus Mortuga died. The room is small, and the victim was found in a "locked room" scenario, making the investigation particularly challenging.

Evidence Found at the Scene:

  • The Blood Trail: Runs from Mortuga's neck toward the back of the room before pooling.
  • Moon Vial: A smashed purple glass bottle with a botanical scent, marked with a moon icon.
  • Hand-drawn Poster: Titled "The Stargazing Girl," originally displayed upside down.
  • The Cauldron: An ancient stone vessel with deep scratches on the interior and barnacles on the exterior.
Evidence ItemLocationSignificance
Smashed VialFloorContains purple liquid, contrasts with Sun Tablets.
Stone CauldronCenterPreviously locked for years, now mysteriously open.
SailclothWallFeatures a drawing of a girl stargazing.
Upside-down PosterPipeMentions 'Lady of the Looking Glass' at Fortuna Hall.
Critical Deduction

Mortuga was alone in a locked room with no weapon found. The only other object in the room is the stone cauldron. Examine the interior scratches carefully; they suggest something was trying to get out.

Final Deductions and Demo Conclusion

The demo concludes with a deduction sequence where Grimoire must piece together how Mortuga died. You must link the state of the cauldron to the cause of death.

Key Deduction Points:

  • Mortuga died from a clean cut across the throat.
  • No bladed weapon was present in the room.
  • The cauldron was recently unlocked for the first time in history.
  • Conclusion: Mortuga unlocked the cauldron and was killed by whatever was inside.
Final Step

After the deduction, the demo ends with the title "Chapter 1: The Curse in the Cauldron." Ensure you have interacted with the "Wooden Boy" figurehead on the deck earlier, as its glowing eyes are the final piece of the environmental puzzle regarding the green light.

Q: Where do I find the code for the serpent cabinet?

There is no written code. You must count the sides of the geometric shapes on the dials. The solution involves matching the number of sides (3, 4, 7, 9) to the dial positions.

Q: What is the significance of the Moon Vial?

The Moon Vial is purple and has a botanical scent, differing from the Sun Tablets found in the Mess Hall. Its presence at the crime scene suggests Mortuga was using a different type of medicine or substance before he died.

Q: How do I get into the submarine control room?

In the demo, the control room is permanently locked. You must follow Captain Seafoam's instructions on the note and proceed to the lower deck to investigate the Illusion Theater instead.

Q: Is there a weapon to find in the Illusion Theater?

No. The mystery of The Mermaid Mask demo walkthrough is that no weapon exists in the room. The deduction suggests the killer or the 'weapon' came from inside the stone cauldron.