Park Chang-ho is known since his school days as "Big Mouth" because he talks big and promises big things but cannot follow it up. He is also an infamous lawyer with a very low rate of success who was hired by a mayor because of his incompetence. Unfortunately, he was framed as the notorious and mysterious swindler "Big Mouse" and sent to prison. Go Mi-ho is Chang-ho's loving wife who works as a nurse. She has strong personality and will do anything to prove the innocence of her husband and help solve the case the mayor has given to her husband. Will Mi-ho be successful in proving her husband's innocence? Or will her investigations lead to opening a can of worms?