How Long To Beat
Estimated completion times for main story, 100% achievement runs and speedruns.
Playtime estimates
| Playstyle | Estimated Time | Notes | | --- | --- | --- | | Main story only | 5–6 hours | Core investigations and required deductions | | Completionist | 8–10 hours | All 21 achievements, optional rooms, every hidden clue | | Guided / speedrun | 3–4 hours | Skipping optional dialogue and using direct solutions |
Getting stuck on complex puzzles like the typewriter ring code or switchboard cables can add 1–2 hours if you avoid hints. The in-game hint system has no penalty, so use it freely to stay on pace.
Achievement categories
| Category | Count | Examples | | --- | --- | --- | | Story progression | 5 | The Beginning, Case Closed (names to be confirmed) | | Puzzle solving | 10 | Cabinet Cracker, True North (names to be confirmed) | | Exploration & collection | 6 | No Stone Unturned, Evidence Collector (names to be confirmed) |
Some achievements are missable, especially those tied to Dirk's phone, Mariana's dictaphone recordings and optional room puzzles. Keep a save before the final reconstruction.
Sources: themermaidmask.wiki, 2026-07-18; ninewiki.com walkthrough, 2026-07-17; Steam Store API (appid 1696770), fetched 2026-07-19.