At seventeen, math prodigy Shang Yihuai tutors a quick-witted girl named Liang Xia through a long summer of equations and margins full of things neither of them says out loud. Weeks before the college entrance exam he vanishes, leaving behind a notebook and a promise about Beijing that he never keeps. Eight years later, fighting to reclaim her parents' old house, Liang Xia takes the name Shen Sang and agrees to a contract marriage she wants no part of. The man she ends up married to is Shang Yiheng, cold and remote at the head of a company, and she has no idea who he really is.