Investigation Mechanics for Horror RPGs

Running successful investigation scenarios requires understanding how players discover information and reach conclusions. This guide covers proven techniques for investigation-focused play, usable in any system.

🔍 The Three Clue Rule

Core Principle: For any conclusion you want the PCs to make, include at least three clues.

Why Three Clues?

Mystery scenarios fail when players miss crucial information. A single clue becomes a chokepoint—if they don't find it or understand it, the adventure stalls. The reality of investigation gameplay:

  • Players will likely miss the first clue entirely
  • They'll overlook or dismiss the second clue as unimportant
  • They'll misinterpret the third before reaching the correct conclusion
  • Multiple clues provide redundancy and prevent single points of failure

Example Implementation

Conclusion: "The killer is Dr. Harrison's former lover, Elena"

Three Different Clues:

  1. Love Letters: Stack of passionate letters in Dr. Harrison's desk, signed "E"
  2. Diary Entry: Victim's diary describing a secret affair and recent bitter breakup
  3. Photographs: Hidden photos showing Dr. Harrison with Elena at romantic locations

Key Benefits

For Players

  • Feel smart for piecing together evidence
  • Have backup options if they miss one clue
  • Experience "aha!" moments naturally
  • Investigation progresses at good pace

For GMs

  • Prevent investigation from stalling
  • Track what players have discovered
  • Introduce new clues when needed
  • Maintain mystery without frustration

📊 Clue Hierarchies

Not all clues should be equally difficult to find. Organize clues into hierarchies based on discovery difficulty. This creates a sense of progression and rewards thorough investigation.

🟢 Obvious Clues

Investigators notice immediately without searching

  • Dead body in middle of floor
  • Blood trail leading to door
  • Strange symbols on walls
  • Loud supernatural sounds
  • Recently disturbed grave

🟡 Hidden Clues

Require active searching or investigation

  • Documents in locked drawer
  • Bloodstains cleaned but visible
  • Scratches on floorboards
  • Hidden compartment in desk
  • Faint footprints in dust

🟣 Expert Clues

Need specific knowledge or skills to recognize

  • Medical cause of death
  • Occult symbol meaning
  • Chemical composition analysis
  • Ancient language translation
  • Forensic evidence interpretation
💡 Design Tip: Include clues from each category for important conclusions. Even if players lack expert knowledge, obvious and hidden clues ensure progress.

🎈 Floating Clues

Floating clues aren't tied to specific locations or actions. The GM introduces them at their discretion when players need a push in the right direction.

How Floating Clues Work

  • Preparation: Designate 2-3 clues as "floating" for each major conclusion
  • Deployment: Introduce when players are stuck or heading down wrong path
  • Delivery: Present through active events (NPC contact, discovery, attack)
  • Integration: Make it feel natural, not like GM intervention

Floating Clue Examples

  • Witness Appears: Surviving victim suddenly contacts investigators
  • Enemy Attack: Cultists attack, revealing their connection to the mystery
  • News Report: Radio announces related incident in different location
  • Anonymous Tip: Mysterious note pushed under door at hotel
  • Chance Encounter: Run into suspect in unexpected location
⚠️ Use Sparingly: Floating clues are a safety net, not a crutch. Players should earn most discoveries through investigation.

⚙️ Investigation System Approaches

Different horror RPG systems handle clue discovery differently. Understanding these approaches helps you run investigations in any system.

Roll-to-Find Approach

Roll to Find Clues

  • Players roll skills to find clues
  • Failed rolls = clue missed (potential stall)
  • Creates tension and stakes
  • Requires Three Clue Rule implementation

Best for: Groups comfortable with potential dead ends; atmospheric horror

Always-Find Approach

Automatic Clue Discovery

  • If you look in right place, you find clue
  • No failed skill rolls for core clues
  • Keeps investigation moving forward
  • Spend points for extra information

Best for: Story-focused groups; investigation-heavy campaigns

💡 Hybrid Approach: Use automatic discovery for vital clues, skill rolls for bonus information or shortcuts. This prevents stalls while maintaining mechanical engagement.

💡 Practical Investigation Tips

Preparation

  • List all conclusions before session
  • Create 3+ clues per conclusion
  • Mix clue difficulty levels
  • Prepare 2-3 floating clues
  • Map out clue locations

During Play

  • Track which clues were discovered
  • Accept creative investigation approaches
  • Reward clever thinking
  • Introduce floating clues if stuck
  • Never punish thorough investigation

Common Mistakes to Avoid

  • ❌ Single clue per conclusion
  • ❌ Hiding clues behind specific actions
  • ❌ Deliberate red herrings
  • ❌ Requiring specific skill uses
  • ❌ Making players guess exact location

What to Do Instead

  • ✅ Multiple paths to each truth
  • ✅ Reward any reasonable approach
  • ✅ Let players create own theories
  • ✅ Accept equivalent skill usage
  • ✅ Generous area searches succeed
✓ Golden Rule: The mystery should be about piecing together information, not about finding information. Make discovery easy; interpretation challenging.

📚 Further Reading

Learn more about investigation design: