Jul 15, 2026

The Mermaid Mask: Prologue Walkthrough

Saad Bin Asif

Welcome to our The Mermaid Mask prologue walkthrough covering all of the puzzles.

The Mermaid Mask is a murder mystery, visual novel-esque, point-and-click game where you’re tasked to solve an “impossible locked-room murder” of Captain Mortuga inside an ancient cauldron. If you’re looking for further information about the game, check out its Steam page right here.

Prologue – The Beginning

Prologue – The Beginning

We wake up at the Stonetop Inn, where our partner, Sally, is sleeping on the mattress. First, click on the book on the floor near Sally. It’s a fantasy novel called Hex of the Helmsmen. Then, click on the red book on your right, which is a Case File, and there’s everything you need to know about the case our protagonists are working on.

It reveals the details of Captain Mortuga’s death. He locked himself in a room, and when someone forced it open, they found his dead body inside. Captain Seaform, the second captain of the Mortuga Submarine, has written everything he knows about the murder in the file; he’s the one who has hired Sally and Detective Grimoire.

See the button on the bottom right? Use it to keep track of the individuals you have met so far. Once you close the case file, Grimoire will hear someone outside. Interact with Sally to wake her up, and with this, you will be free to explore different locations; don’t forget to click on all the items to find all the clues.

Use the map button on the bottom-left screen, then click the question mark rectangle to enter the Town Square.

Town Square

The Town Square is gloomy and features a fountain and multiple abandoned buildings. Click on the signs to learn further about the environment, and then talk to Sally.

However, there’s something off here. There’s a gloomy green light coming from the water. Click on it, and when Grimoire comments about its “weirdness,” a submarine will show itself. After you’ve checked everything in the town square, interact with the submarine to board it.

Submarine – Fore Deck

The submarine’s fore deck reeks of gloominess with the wooden buoy on the floor. Check it, and Sally and Grimoire will comment on its ability to emanate light from the carved eyes.

Sally says it works exactly opposite to a lighthouse, which is an indicator to tell a captain to stay away, but this specific wooden buoy lured the detectives in with its light.

Now, click on Sally to enter the submarine; an eerie screech will be heard before you descend the staircase. Grimoire asks Sally about it, but she is clueless, as he’s the only one who heard it.

Submarine – Parlor

As Sally and Grimoire enter the submarine, they can’t see a thing due to pitch-black darkness. Luckily, Sally stumbles upon a lever and uses it to light up the whole area with a pink flame.

The Parlor feels lively. There’s an unfinished wine glass, confirming the signs of life in this gloomy submarine. There isn’t anything interesting to interact with. So, to continue with the murder mystery, click on the door leading to the control room.

However, it’s locked. Take a peek inside through the glass, but there’s a piece of paper blocking it. On the paper, Captain Seafoam tells the detective duo to stay away from the control room and the floor where the murder took place. Sally thinks that the captain is hiding from them, but Grimoire feels the opposite.

Open the map to find four new available locations. Head to the floor below before exploring any other rooms.

Submarine – Mess Hall

The Mess Hall is a complete… mess. There are multiple cards spread across the table, indicating that someone lost badly and threw them in anger. Interact with the pots, pans, lamps, candles, and lastly, the snake-shaped cabinet.

Look closer into the cabinet to initiate a puzzle where you have to put four dials into the correct positions. Below you will find the solved screenshot.

Puzzle Information: There are three types of shapes - Triangle (3), Square (4) , and Pentagon (5). And in the dials, there are four different numbers - 3, 9, 7, and 4. To solve this puzzle, put the exact number of corners inside one window. For example, put a Triangle and Pentagon in the window with 9. However, the tricky part are the dials; they all have three shapes. But, with the image above, you can easily solve it.

Inside the cabinet, the detectives find a bottle of Sun Tablet with three varieties of tablets. With the room Mess Hall all investigated, click on the map button to find eight new rooms. Before you can explore further rooms, head to the right-most room on the map.

Submarine – Illusion Theatre

This is where the murder took place: the illusion theatre. Inside, you will find the cauldron where Mortuga was resting and his blood stain from the neck wound.

Interact with the Cauldron to find numerous deep scratches inside it. Then, there’s a broken bottle with an engraved moon symbol on it. Now, click on the broken stool, and then select Stonetop Inn. The stools at the inn and this theatre are exactly the same, which ultimately connects these places.

Click on the ragged cloth to your right that reads “The Stargazing Girl,” on its back. Then, check the poster to the left in the theatre. It was stuck on the wall upside down. If you notice, the poster shows the angel of death attacking someone in a bowl, which is shaped exactly as the cauldron where Captain Mortuga’s body was found.

Finally, click on the chalk outline. It prompts Grimoire to cautiously think about what happened to Mortuga, and considering how small the cauldron room is, there’s no place for the killer to hide, but there is.

Here, you will be greeted with a clue connection screen. To solve it, here is what you have to do:

“Magnus Mortuga Unlocked The Cauldron And Was Killed By What Was Inside.”

However, Sally finds it hard to believe since, according to the case file, the cauldron has stayed shut since the beginning. But Grimoire counters her point, saying that there’s something inside it.

Now, when you get to the “I noticed Something” section, rotate the cauldron and move the cursor on the scratches.

Sally is confused about the scratches inside the cauldron.

As she thinks about it, the prologue ends, and the murder mystery properly begins.

Here, our The Mermaid Mask prologue walkthrough comes to an end. We’ll continue this mystery in the next part! Don’t forget to check out our complete walkthrough hub of this game.

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