One participant. Twenty-one questions. All that is required is the ability to tell the truth, the whole truth, and nothing but the truth.

Six couples test their trust with an eye-scanning lie detector in this reality series where deception costs money, and the truth comes with a prize.

This drama is about various contestants who take part in a game show with a prize of 10 billion won wherein contestants are encouraged to cheat and lie. The contestants who able to cheat the others will wins the prize but but be in debt if he/she loses the game. Contestants include genius swindler Cha Woo-jin and naive college student Nam Da-jung. Meanwhile, Kang Do-young will play the MC and planner of this game show.

Friends hope to help one another improve by writing anonymous letters with detailed instructions.