Once per round, each player may accuse another player of being the Spy. If all players agree, the game ends and that player’s secret card is flipped up. If the Spy is captured, each of the Non-Spy players win the round. If a Non-Spy is revealed, the Spy wins. Finally, if the Spy figures out where they are, they can reveal their card and make a guess. If they’re right, they win the round. If not, the Non-Spy players win.
The game is played over a series of rounds and points are awarded each round. A complete game is typically five rounds and the cards are randomly dealt each round. You could even be the Spy two rounds in a row! After the last round, the player with the most points is the winner.