General Overview and Tips

The Mermaid Mask sends Detective Grimoire and Sally into the Mortuga Submarine, where every room seems to contain either a secret or a nautical object designed by someone with a grudge against common sense. Your job is to explore rooms, question suspects, inspect evidence, and turn those findings into deductions. The best part is earning the conclusion yourself: noticing one odd detail, testing a theory, and watching an impossible mystery become perfectly possible.

Later in the case, the Case File can look like someone tipped a detective’s tackle box across the floor. When the next clue refuses to stand out, do not sweep the whole submarine at random. Choose the suspect, clue, or deduction that has stalled, then review its recent entries and recorded responses. If the link is still unclear, use the optional hint attached to the investigation. One focused check is usually more useful than another grand tour of the vessel.

How the Investigation Fits Together

Explore the submarine. Search each available room and inspect details tied to the victim, a suspect, or the locked-room mystery.
Question the suspects. Work through useful topics and return after finding new evidence. Fresh clues can open more questions, clue reactions, and Suspicion confrontations.
Check the Case File. This is your working notebook. It stores collected clues, suspect entries, testimony, and recorded reactions so you can compare stories and find unfinished links.
Inspect 3D clues. Collected objects can be rotated and, when controls appear, manipulated. An important detail may sit underneath, behind a flap, inside a compartment, or on a part that first looked decorative.
Complete deductions. These logic checks may ask you to fill a blank, assemble a statement, select a clue, or connect a conclusion to supporting evidence. Build the answer from what Grimoire and Sally have recorded instead of relying on story instinct alone.

These systems form a loop. Exploration produces evidence. Evidence changes conversations. Conversations point back to rooms or objects. The Case File gathers those threads, and deductions test whether they fit. If a Suspicion option remains locked, you normally need more evidence, another clue reaction, or an unfinished conversation.

Inspect Every Side of a Clue

Whenever a collected clue opens as a 3D object, rotate it through every angle. Look at the top, bottom, back, and narrow edges. Test visible hinges, switches, lids, labels, catches, buttons, and loose parts. Open anything that appears movable, then rotate the changed object again. If a clue contains pages, messages, recordings, or navigation arrows, use the available controls to review the full contents.

Move slowly when the object has small parts. A dark switch against dark wood can vanish like a submariner at washing-up time. This is a reliable search habit, but it is not a guaranteed solution to every puzzle. Some devices only make sense after you find a matching clue or hear the right testimony.

Rooms, Routes, and Progression

Rooms can often be explored in different orders. If several locations are open, choosing one first will not ruin the investigation. Treat any suggested route as a way to reduce backtracking, not as the only legal voyage. Progress still depends on fixed triggers: a required clue, puzzle reward, conversation, confrontation, or deduction may need to be completed before the next location or event appears.

If a door, topic, or deduction stays unavailable, check the related evidence chain before assuming the game is stuck. Review the relevant suspect and clue entries, fully inspect recent evidence, and speak again with the person connected to it. You should not need to restart simply because you explored the open rooms in a different order.

Flavor or Case File Clue?

The Mortuga Submarine is packed with clickable scenery and dry comments from Grimoire and Sally. Not every joke, ornament, or suspiciously elaborate lamp is mandatory. Important evidence is added to the Case File, becomes available as a conversation topic, changes an investigation, or feeds into a puzzle or deduction. If an interaction only produces banter and creates no clue entry or other change, treat it as flavor. Enjoy it, but do not assume every clickable object must be cleared.

When You Are Stuck

Open the Case File and choose the stalled suspect, clue, or deduction.
Review its recorded reactions and check for an unread topic or optional hint.
Reopen the linked clue and examine every face, movable part, page, message, or recording.
Return to the room where the clue was found and inspect anything that has changed or was previously closed.
Question the linked suspect again, use any new topic, and then check the deduction or Suspicion screen.

This short loop is especially useful when your Case File is crowded. It turns “I have fifty clues and no idea what the game wants” into a clean check of one room, one person, and one piece of evidence.

For spoiler control, this walkthrough separates help into three layers. Stop as soon as the case clicks into place.

Hint

The Hint layer points to the room, object, suspect, or testimony that deserves another look. Start here if you want a nudge while keeping the aha moment intact.

Reasoning

The Reasoning layer explains the rule or clue connection. Use it when you found the right material but cannot see why the pieces fit.

Answer

The Answer layer gives the exact manipulation, selection order, or accepted deduction when a concrete blocker needs clearing. It may reveal puzzle results or story details, so move into it only when you are ready. Culprit, motive, method, and final-timeline revelations remain behind their own clear spoiler boundary.