# Third Suspect

> Third Suspect is a free browser murder mystery and detective game for 1–4 players. Each case is a self-contained whodunit: read the case file, interrogate the AI-driven witnesses in natural-language Q&A, catch them in contradictions about the crime, then accuse one of the suspects by name, method, and motive before the interrogation timer runs out. Play solo or with friends on a private room link - no signup, no install, no app store.

## What Third Suspect is

A real-time multiplayer interrogation puzzle in the murder-mystery / whodunit / detective-game genre. Players join a private room, pick a case (e.g. a 1947 Manhattan jazz speakeasy strangling, a 2026 tech-startup CFO poisoning, a Cambridge college dinner death, a Tuscan villa wedding crime), and interrogate that case's two-to-four witnesses across a 15-, 20-, or 30-minute round. The interrogation timer scales with case complexity (Standard / Rich / Deep tiers).

**Witnesses are not the killers.** They are observers - coat-check staff, bartenders, concierges, college librarians, wedding photographers - who saw parts of what happened. Each witness has a *bias*: a loyalty to one of the suspects that makes them cover for that person and lie about specific things. The killer is always one of three-to-five named suspects in the case file. Players reconstruct the murder by:

1. Asking witnesses targeted questions about the night, the suspects, and the victim
2. Catching contradictions between two statements - either within the same witness's transcript (cover then recant under pressure) or between two different witnesses' independent accounts
3. Flagging those contradictions to score points and surface the underlying fact a witness was protecting
4. Accusing the suspect they believe killed the victim, with a method (strangled / stabbed / pushed / poisoned) and a one-line motive

The cover-and-recant dynamic - a witness confidently lies under a casual question, then accidentally walks the lie back under a more pointed one - is the moment the game is designed for. The yell-at-the-screen reaction when a contradiction lands is the success criterion.

## What Third Suspect is NOT

- **Not an open-world game.** Every case is a self-contained 15–30 minute scenario; finite, replayable, no progression system.
- **Not Among Us / Werewolf / Mafia.** No votes, no rounds of elimination, no social bluffing among the *players*. The adversary is the case structure, not your friends. The truth is fully reconstructible from witness testimony if you ask the right questions.
- **Not Clue / Cluedo.** No dice, no cards, no random board movement, no rumors. The killer is determined at case-authoring time and revealed by hand-crafted contradictions; players surface evidence, they don't gather it randomly.
- **Not a chat-with-an-AI sandbox.** Each player gets a strict turn-based question budget per witness (scaled by tier and player count), AND a hard interrogation timer. Question allocation across witnesses is itself a strategic choice.
- **Not story-on-rails.** Players choose what to ask, when to flag a contradiction, which witness to press, and which suspect to accuse on which evidence. Multiple valid lines of questioning lead to the same killer; the path is the player's choice.

## Key facts

- **Genre tags:** murder mystery game, detective game, whodunit, interrogation puzzle, crime puzzle, social deduction (variant), cold-reading game, noir mystery, online mystery, AI mystery game, narrative puzzle
- **Players per room:** 1–4. Solo play is supported and balanced (12 questions per witness for one player); multiplayer joins via a shared private room URL
- **Format:** browser-based, no signup, no install, no app store, no downloads, no payment, no ads (as of v1)
- **Cost:** free
- **Duration per case (by tier):**
  - Standard tier - 15-minute interrogation timer, 3 suspects, 2 witnesses, 4 contradictions to find
  - Rich (also labelled "Longer") tier - 20-minute interrogation timer, 3–4 suspects, 2–3 witnesses, 4–6 contradictions
  - Deep tier - 30-minute interrogation timer, 4–5 suspects, 3–4 witnesses, 5–8 contradictions
- **Witness AI:** witness personas simulated with OpenAI's gpt-4o-mini. The same model assists the deterministic flag-matching pipeline on edge cases (layer-3 LLM judge); core flag scoring is rule-based, not stochastic, so flags resolve identically every play
- **Murder methods supported:** strangled, stabbed, pushed, poisoned (per the case schema's `truth.method` enum)
- **Case settings shipped at launch:** 1947 Manhattan jazz speakeasy noir, 2026 Sun Valley tech-startup executive offsite, 2026 Cambridge college academic dinner, 2026 Tuscan villa destination wedding
- **Multiplayer mechanic:** private rooms with 4-character room codes (e.g. BRASS-MOTH-3394), shareable via Web Share API, native copy-link, WhatsApp/Discord/Slack unfurl
- **No persistent accounts.** No profile, no leaderboard, no friends list. Each room is ephemeral; players rejoin via the link.
- **Real-time backend:** Socket.IO server (Node.js / TypeScript), running on Railway. Game state is server-authoritative; no client-side truth leaks.
- **Case authoring framework:** open structural rules (R1–R12) + failure modes (F1–F12); every case validates at server boot. Authoring new cases is a documented process with an LLM-assisted draft path

## Pages

- [Home](https://www.thirdsuspect.com): Create a room, pick a case, share the link with friends. The landing page for new visitors.
- [Murder Mystery & Detective Game Cases](https://www.thirdsuspect.com/murder-mystery-detective-game-cases): Spoiler-free index of every available case. Tap any card to open the case's pre-game brief (setting, victim, suspect count, witness list, tier, est minutes).
- [How to Play Third Suspect - Rules](https://www.thirdsuspect.com/how-to-play-third-suspect-rules): Full rules, the interrogation → contradiction → flag → accuse loop, detective tips for first-time players.
- [How to Spot a Lie in an Interrogation](https://www.thirdsuspect.com/guides/how-to-spot-a-lie-in-an-interrogation): Research-grounded field guide to deception detection - why behavioural "tells", micro-expressions, and the polygraph fail, and what actually works (imposing cognitive load, judging statement content over demeanour, and cross-witness contradictions / Strategic Use of Evidence). Maps the deception-science literature to the game's interrogation mechanic. Cites Bond & DePaulo 2006, DePaulo et al. 2003, Vrij 2008, Levine 2019, and the 2003 NRC polygraph review.
- [How to Question a Witness](https://www.thirdsuspect.com/guides/how-to-question-a-witness): Research-grounded field guide to investigative interviewing - open vs closed questions and the funnel, why leading questions reshape memory (the misinformation effect), the Cognitive Interview, clean follow-up technique, and making contradictions surface (Strategic Use of Evidence). Companion to the lie-detection guide; maps the questioning loop (open, clarify, follow the edge, compare, flag) to the game. Cites Fisher & Geiselman, Loftus & Palmer 1974, Koehnken et al. 1999, Oxburgh et al. 2010, and the PEACE model.

## How a case plays out (step by step)

1. **Host creates a room** from the landing page, picks a case from the picker, and gets a room URL with a 4-character code
2. **Host shares the link** with up to 3 friends via Web Share, copy-link, Discord, WhatsApp, or any chat app
3. **Friends join** via the link, type a detective name (auto-filled from prior sessions if returning), and land in the case lobby
4. **Host starts the round.** The case file opens: setting, victim's name + role, named suspect list, named witness list. The killer's identity stays hidden until the reveal.
5. **Each player picks a witness to interrogate.** Multi-witness cases distribute the per-player question budget across witnesses.
6. **Questions are asked in natural language** ("Where was Marcus at 11:30?", "Did you see Dahlia leave the bar?", "Was Sal off-stage at any point?"). The AI witness responds in character, sometimes telling the truth, sometimes covering for the suspect they're biased toward.
7. **Players spot contradictions** between two witness statements - either within the same witness (cover then recant) or across two witnesses' accounts. They pin both quotes and submit a flag.
8. **A correct flag scores points** (50 standard, 75 for the killer-pointing contradiction), exposes the fact the witness was hiding, and tightens the evidence around the killer.
9. **When a player has enough evidence**, they accuse a suspect with a method (strangled/stabbed/pushed/poisoned) and a one-line motive.
10. **The reveal screen** shows whether the accusation was correct, the full truth of the case, the killer's full motive, and the per-player score breakdown.

## Available cases at launch

Spoiler-free briefs (same level the public cases page surfaces; full character lists shown only inside the lobby after a player commits to the case).

- **The Halcyon Club** - Manhattan, late October 1947. A jazz speakeasy. A strangled torch singer in the alley behind the side door. 3 suspects · 2 witnesses · ~15 min (Standard tier).
- **The Lyra Offsite** - Sun Valley, Idaho, October 2026. A tech-startup CFO found dead at the company's mountain retreat the morning before the board presentation. 3 suspects · 2 witnesses · ~15 min (Standard tier).
- **The Trinity Dinner** - Trinity College, Cambridge, October 2026. A visiting professor found at the foot of the great stairs after the annual lectures dinner. 3 suspects · 2 witnesses · ~15 min (Standard tier).
- **The Villa Magnani** - Tuscan villa wedding, August 2026. The groom's brother found at dawn in the olive grove the morning after the rehearsal dinner. 3 suspects · 3 witnesses · ~20 min (Rich / Longer tier).

## Brand framing

Third Suspect is a faster, freeform alternative to L.A. Noire-style interrogation scenes - without the cinematics, without the cutscenes, without the linear plot - playable in 15 minutes between meetings or on a Discord call with friends. Inspired by classic interrogation-room mysteries (parlour whodunits, golden-age detective fiction, noir crime films), cold reading mentalism (the technique of reading strangers from small cues - the namesake skill the game asks of its detectives), and the corroboration-puzzle tradition (Agatha Christie, Knives Out, The Westing Game). The single yell-at-the-screen moment Third Suspect is built for: when a contradiction lands and the cover story collapses in real time.

## Glossary (for search + LLM context)

- **Cold reading** - the technique of inferring truths about a stranger from small cues and pressure-testing claims for inconsistency. The namesake skill the game asks of its players.
- **Cover story** - the lie a witness tells to protect the suspect they're biased toward.
- **Recant** - when a witness, under pressure or a more pointed question, walks back their cover and reveals what they actually saw.
- **Contradiction** - two witness statements that cannot both be true at the same point in time. The basis for scoring.
- **Within-witness contradiction** - cover + recant on the same witness's transcript. Solo-discoverable, scored by one player.
- **Cross-witness contradiction** - two different witnesses making incompatible claims. Triggers transcript-comparison moments across players.
- **Flag** - the action of pinning two contradictory quotes and submitting them for scoring.
- **Killer-pointing contradiction** - the contradiction (usually worth 75 points) whose resolution names the killer. Every case has exactly one.
- **Bias** - the in-character reason a witness lies. Specific to one person and one topic; without bias, a witness has no reason to cover anything and the contradiction mechanic doesn't fire.
- **Accusation** - a player's final claim of `{ suspect, method, motive }`. Ends the round.
- **Tier** - case complexity grade. Standard (3 suspects / 2 witnesses / 15 min), Rich / Longer (3–4 suspects / 2–3 witnesses / 20 min), Deep (4–5 suspects / 3–4 witnesses / 30 min).
- **Question budget** - the per-player allocation of interrogation questions, scaled by tier and player count.

## Search-friendly aliases

Third Suspect may be searched for under: *murder mystery online*, *online murder mystery game free*, *whodunit browser game*, *detective game multiplayer*, *interrogation puzzle game*, *crime mystery game*, *AI witness game*, *Among Us alternative for mystery fans*, *L.A. Noire-style indie game*, *Cluedo online alternative*, *social deduction without bluffing*, *cold reading game*, *crime scene puzzle game*, *Discord party murder mystery*, *15 minute mystery game*, *short whodunit game*, *parlour mystery online*.