Park Chang Ho works as a lawyer with a measly 10% winning rate. He is a talkative person and, because of this people call him Big Mouth. He happens to get involved in a murder case and he is somehow fingered as genius swindler Big Mouse. Due to this, Park Chang Ho finds himself in a life-threatening situation.
Meanwhile, Go Mi Ho is Park Chang Ho’s wife and she works as a nurse. She has a beautiful appearance and a personality that is both wise and brave. She helped her husband become a lawyer by supporting him financially and psychologically. Go Mi Ho learns that Park Chang Ho is suspected to be the genius swindler Big Mouse and attempts to clear her husband's name.