P.I. is a pure deduction game, with players competing in three consecutive mini-games in order to see who's got the best chops in terms of solving their cases.
Each mini-game plays out the same way. To start, you receive in secret one suspect card (out of 12), one crime card (out of 10), and one location card (out of 14); this set of information represents the case that the player to your left must solve. The game board shows fourteen locations arranged so that each location touches a few others; each location has space for a suspect and crime tile. Shuffle the suspect tiles (12, plus two "no suspect") and the crime tiles (10, plus four "no crime"), then place one face up in each location. Each suspect, crime and location is included in a deck of evidence cards, and nine evidence cards are revealed.
Whoever has the most points after three mini-cases wins.