What is Nancy Drew till death do us part all about?

In "Till Death Do Us Part", Ned has been acting distant towards Nancy (not going out with her for a month or two) and it turns out that he's been involved with another girl, Jessica Thorne. But, don't worry, he's still totally into Nancy! They'd had an argument that Ned might as good a detective (or better) than Nancy and he sets out to prove his detective abilities, because he suspects something's up with Jessica. Something is indeed up with Jessica - to whom Ned becomes engaged - who plans to kill Ned and try to pass him off as her dead husband so she can collect her husband's inheritance. (Her husband Scott hated being married to her and left her about six months after their wedding.) But Nancy catches Jessica and is truly reunited with Ned in the end! (Ned never considered his engagement with Jessica real because he only asked her to marry him to keep from blowing his cover. And he did propose to Nancy first. When he realized he'd have to ask Jessica to marry him, he decided to keep a promise he'd made to himself that Nancy Drew would be the first girl he'd ever propose to.)