In Mr. Jack, one of the two players is Jack the Ripper, who is one of the 8 characters on the board. This player is aware which character is Mr. Jack, and his goal is to flee from the district as soon as possible (or avoid being accused for eight turns). The other player represents an independent investigator (not represented on the board) who attempts to guess the identity of Jack — but he can make only one guess during the game!
During each turn, the players move the characters, using their unique powers and placing them either in shadow or light. At the end of each turn, the witnesses declare if Jack is visible — that is, in light or adjacent to another character — or not (alone in the shadows). This lets the investigator know which characters are innocent. As the turns progress, the investigator attempts to eliminate suspects while Jack tries to escape. Intuition, logic, and cold blood is needed for each of the two participants.