G1S1 - Whodunnit?
The series follows 13 guests, one of whom is secretly the "killer" posing as a contestant in the game, living in a Beverly Hills mansion named Rue Manor. They are guided by the butler, Giles. The guests, along with Giles and two maids, are trapped by the killer within the house grounds until they determine who the killer is. Giles acts as a puppet for the killer; the killer sends messages to Giles, who reads them to the surviving guests.
Each episode, at least one guest is "murdered" by the killer, either while the victim is alone or through pre-arranged circumstances while the remaining guests are congregated as to avoid revealing their identity. After the shock of the event, Giles offers the remaining guests an opportunity to search one of three areas (usually the crime scene, the last known whereabouts, or the morgue containing the victim's body) to discover clues about how the murder was carried out. Guests are free to select which area to search, though they are allowed access to only one area with a limited amount of time. Guests then participate in a riddle challenge that leads them in a competitive search through the mansion. The guest who is able to complete the challenge receives an additional clue that may greatly help in solving how the murder was committed.
Guests are given limited opportunities to congregate, where they can share, withhold, or lie about whatever information they find from their investigations and riddle challenges; at all other times, guests are isolated from each other.
Later, guests are individually taken to the mansion library where they describe to the unseen killer how they believe the murder took place and make an accusation as to who the killer is. However, each elimination is actually based on the guests' performance on an unaired written quiz (similar to The Mole) that objectively assesses the accuracy of their theories. The quiz consists of 12-15 short answer questions about the investigation sites and the riddle challenge; ties are broken based on the time taken to complete the quiz.
During dinner, Giles presents a message from the killer. The message states which guest had the most correct theory and is subsequently spared from being the killer's next victim. The message then fully explains how the murder was completed. After this, Giles hands an envelope to each remaining guest. Those receiving cards with the word "Spared" performed well enough to advance to the next episode. The lowest-scoring guest, along with at least one other low-scoring guest will receive a card with the word "Scared." As noted above, the guest playing the killer is as unaware of how the murders are committed as the rest of the guests are, and so may also receive a "Scared" card as well; however, the killer cannot be eliminated. The lowest-scoring guest is then eliminated from the competition by being "murdered by the killer", in turn setting up the murder to be solved in the next episode.
In the finale, the final three guests (the killer and the two remaining players) compete in a multi-part riddle and memory challenge.