一桩有预谋的杀人案令三流律师“大嘴巴”朴昌浩（李钟硕 饰）一夜之间成为天才诈骗犯“大老鼠”，被诬陷进入狱黑化成为监狱大佬，以恶制恶同黑暗势力对抗。妻子高薇瑚（林允儿 饰）为拯救丈夫，同他里应外合共同查案，夫妻二人誓要揭出幕后黑手。
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.
