In Sleuth, the Dealer shuffles the Gem Deck and removes one card, placing it where no player may accidentally see it. This becomes the Missing Gem. The remaining Gem cards are dealt evenly to each player to form their hands. Players record the information from their private cards on their information sheets. Any remaining Gem cards are placed face up for all players to note and record on their information sheets.

Each Gem Card has three elements:
-Gem (diamond, pearl, or opal)
-Color (red, yellow, blue, or green)
-Type (solitaire, pair, or cluster)

Players use Search Cards to discover and record what their opponents hold in their hands-i.e. if a player had the "Blue Opals" search card, he could request any other single player show them all the blue opals in their hand. Other search cards have only one characteristic "element" of a gem-i.e. just opals, or just blues. With these cards, the interrogated player must reveal only the number of these cards that they hold and not reveal the cards themselves.

Play continues until one player believes they have solved the mystery. They note their guess and check the missing gem. If correct, the player reveals the card and wins the game! If incorrect, the player replaces the missing gem and the game continues. This player is now out of contention but must continue answering any interrogations.