Hae-Sol has an innocent appearance and a sad past. She meets Jinhyeong while volunteering, and when their love blossoms, she marries him. However, Hae-Sol never expects Jinhyeong to be a hitman in disguise. Unable to accept her husband's profession, Hae-Sol divorces him and opens a guest house to make a living. Coincidentally, her ex-husband and first love declare they will move into the guest house... Can she overcome this deadly man's fatal flaws? Their romantic and dangerous life under the same roof begins!