Puzzle gaming’s best detective duo are back solving a maritime murder in The Mermaid Mask

Rachel Watts, 1 July 2025

There isn’t a detective duo I love more than Detective Grimoire and Sally (sorry, Disco Elysium’s Harry and Kim, a close second though). When we last saw the iconic pair, they were unraveling a curious case of a painting that had seemingly killed its creator in Tangle Tower. Jump to the present, and the two are now investigating the murder of a submarine sea captain in The Mermaid Mask. But this is a Grimoire mystery, so of course, there’s going to be a strange twist in this maritime tale.

I practically jumped at the game's demo (which you can download and play over on the game’s Steam page) as Tangle Tower is one of the best cosy detective games I have ever played. I love it so much that I make sure to play it at least once a year. There's not a lot of puzzle-solving in the demo, but it’s short, sweet, and gives you more than enough to get excited for in the full game.

Grimoire and Sally have been called out to a battered, salt-swollen seaside town that has seen better days. They’re on a stakeout in a dreary inn when, at four in the morning, they spot a bright green beacon approaching the docks. Like a monster emerging from the deep, they see it’s a submarine and, through the mist, can make out a shadowy figure on deck opening the submarine’s main hatch before disappearing below. The two follow the figure and jump on board, descending into the metallic beast’s rumbling innards. The scene of the crime is nestled among the submarine’s many chambers, so the two board the ship unaware of what they'll find on this mysterious vessel.

When they reach the crime scene, it’s riddled with questions. Captain Mangus Mortuga was found lying on the floor of a small chamber locked from the inside with no other entrances or exits, all that's left of him now is the chalky white outline of where his body was found. An ancient stone cauldron that’s been sealed for hundreds of years now sits open and empty at the back of the chamber. So, who killed Captain Mangus Mortuga? What was hidden away in the cauldron? Why was the room locked from the inside?

It’s a classic locked room mystery but with a mythical, pirate-y twist. There are rumours that the captain was an immortal time traveller, or a vampire, cursed to stay hidden beneath the waves forever. The cauldron itself is an object shrouded in mystery, too. There are scratches on the inside that make it look like something was scrambling to escape. An event poster for a ghostly ‘Illusion Show’ is pinned to the wall, the words “Unfathomable!” and “Inconceivable!” slapped across its centre. It's all ruddy mysterious.

I love mysteries that blur the lines between logic and reasoning with mythos and magic - something supernatural that seemingly can’t be explained. Return of the Obra Dinn's deep sea encounters and The Case of the Golden Idol's cult conjurings are two great examples of this, and the Grimoire games make a fantastic third. Detective Grimoire has always been concerned with mythological mysteries ever since the first game, where Grimoire was called to a murky swampland to solve the mystery of a murderous fabled legend turned tourist attraction. The set-up in The Mermaid Mask hints that this new game will follow the series' love of myths and lore. Everything in the demo points to a handful of underlying themes: dreams, curses, illusion, deception, myths, and legends of the sea.

Exploring the rest of the submarine is an absolute treat. There’s only one puzzle in the demo found in the submarine’s Mess Hall - a light brain teaser about matching a set of shapes to a set of numbers. It's fun and tactile, nothing that will have you reaching for pen and paper just yet. It’s a great indication that SFB is sticking with their tried and true puzzle formula: tactile brain teasers that focus on variation rather than hardcore head-scratchers.

The presentation here is top-notch, too. Just like the other games in the series, each character is fully voice-acted and comes complete with unique character animations and bold visual designs. The backgrounds of areas are bursting with painterly detail, pops of colour breathing life into what could have been a dull and dank submarine. I also love how the evidence in your case file is rendered in 3D, meaning you can turn each object over and inspect every detail to gain more insight, like in the modern Ace Attorney games.

I also really love how SFB approaches fill-in-the-blank puzzles that have grown popular in the last couple of years. The first part of the puzzle is dragging and dropping words into a statement (nothing different there), but what's super helpful is that each character and object has a portrait, so you know exactly what the object is and who is who. It’s super visual and lets you imagine how the events unfolded instead of just reading a paragraph of text.  The second part involves scrolling through a wheel of words to complete the statement, giving you a clear, segmented structure with limited choices. It makes these sections easier, but Grimoire has always been about having a good time than presenting a challenge.

With this approachability in mind, I would, for the most part, call the Grimoire games cosy, but that doesn’t mean there aren't unnerving moments. It’s not so much scary, but a bit creepy, like how in the demo, the wooden buoy looks like a drowned human head, and how the soundtrack is stacked with layers of Gregorian chanting, making your investigation of the crime scene feel like you're intruding on a sacred space.

Thankfully, Grimoire and Sally are there to bring warmth to the more chilly moments. The dialogue and banter between the two is quality, and it’s back in full force in this demo. Their chemistry is unmatched, from Grimoire’s flair and endearing wit constantly met with Sally’s bluntness.

The demo leaves much of the submarine unexplored, but the breadcrumbs have been fully sprinkled, and I've excitedly hoovered up every single one. I also love how with this third game, SFB games have leaned into the episodic mystery releases we’re seeing with the likes of the Frog Detective trilogy, and the more recent Duck Detective duology and Golden Idol Investigation DLCs. I honestly hope SFB never stops making Grimoire games, the detective genre is a better place with them.