Interactive Murder Mystery Party Game

I'm planning a 3-day birthday weekend for twins in their twenties and need a fully tailored, self-running murder mystery across 2 evenings, each building on the last.

The Setting:
A large old house with an Italian palazzo feel – big kept garden, mysterious rooms, hidden corners. The story must be rooted in this specific location. Clues and tasks should be spread across the house and garden to get players moving and exploring. (I can share a video of the property.)

Players:
~23 participants in their twenties, of which 3–5 optional extra characters in case some guests can't make it. Tone: fun, dramatic, a little dark – not childish.

Key Requirement – Fully Self-Running:
No game master. No host. The game runs itself through the players' own actions. A small setup crew will place everything in advance, but won't be present during the game. Everything must be foolproof and self-explanatory from the moment it starts.

What I Need:
- Multi-part storyline across 2 evenings
- Individual character profiles: backstory, secrets, motives, relationships
- Character-specific tasks, clues and prop suggestions (things I can easily prepare myself)
- Setup guide: exactly where to place each clue/prop before the game
- Player instructions per evening – clear enough to need no explanation
- A satisfying final reveal triggered by the players themselves

Deliverables:
- Full print-ready game package (PDF or editable doc)
- Separate document per character