#87: Dial M for Mindflayer | A Mind Flayer Noir Mystery — A 5e One-Shot Adventure for Small Groups
Every friendly face in Blackmire might already be hollow. Find out who is still human — before it finds out who you are.
It has rained on the gaslit dockside city of Blackmire for nine days, and people are vanishing. Not dying — vanishing, and coming back wrong. A grieving noblewoman hires your crew to find her missing husband, and the only clue is the last thing anyone said about him: that he looked "wrong, like his face did not fit." The trail runs through a bought-and-paid-for guardhouse, a madhouse where every patient draws the same tentacled face, and a derelict mill on the docks where something that fell from a dead hive-mind has been quietly wearing the people you trust.
Dial M for Mindflayer is a complete, ready-to-run noir mystery for fifth edition — a social-deduction thriller where the monster does not roar, it smiles. As the night wears on, you track the Thrall Counter while the city falls one mind at a time, use the Loyalty Test to expose who has been replaced, and decide what to do with an illithid artifact that could save your city or damn it. Every ally might be a puppet. Every memory might be a lie. The only people you can trust are the ones you have watched bleed.
This is hardboiled detective fiction crossed with body-snatcher horror: trench-and-lamplight atmosphere, gallows humor, and the slow, grinding dread of realizing you cannot trust your own eyes. The horror here is paranoia, not gore — table-safe, unsettling rather than graphic — and the villain is not a typical monster but a desperate, lonely refugee that hollows out a city simply to stop being alone.
A Mystery You Cannot Fail:
The investigation is built on the 3 Clue Rule, so the truth always reaches the table — your players discover it faster or slower, but never get stuck. Skill checks shape the danger instead of replacing it: expose a thrall before it strikes and you defuse an ambush; trust the wrong face and the city closes in. Combat is mandatory in every act, but clever play makes every fight easier, and the night is cashed in at a climax whose difficulty your players set themselves.
What is Inside:
- A complete 2–3 hour one-shot for 2–3 players at levels 2–3 — zero prep, just open the book and play
- Four acts and eighteen named scenes of hardboiled investigation, with read-aloud narration in every scene
- A branching Act Two that sends your players down one of two routes — a corrupt guardhouse or a sinister asylum — both leading to the same dreadful place
- A signature social-deduction engine: the Thrall Counter that rises as the city is hollowed, and a four-method Loyalty Test for unmasking the impostors hiding in plain sight
- A three-phase boss fight, fully stress-tested at the worst-case table so it never one-shots a hero
- Five original creatures with full fifth-edition stat blocks, four memorable NPCs, and three face-stealing impostors
- Four ready-made characters — any two of them form a complete, viable party
- Five battle maps with Game Master reference points for every encounter
- Six opening hooks, six "what if" contingencies for when players go off the rails, and five campaign seeds for what comes next
- Three distinct endings the players choose for themselves — no right answer, only consequences
Perfect For:
- Busy Game Masters who want a polished, atmospheric one-shot with no prep grind
- Small groups and two-player duos who want a tense, story-driven session
- Tables that crave mystery, paranoia, and creeping cosmic horror instead of another dungeon crawl
- A single-session detour you can drop into any fifth-edition campaign
Everything you need to run a complete session is right here — stat blocks, maps, pregenerated heroes, and a mystery that runs itself. Pour a drink, lock the door, and check the eyes of everyone at the table. Then just add dice.
