“Is it big or small? My future husband’s… manhood, I mean.” According to the era's most scandalous bestseller, a truly great husband must be blessed with both a stunning face and a grand "package." Seo-young, a bride-to-be, takes this advice to heart. In a bold move to vet her fiancé, she ends up asking a complete stranger—whom she mistakes for her future brother-in-law—about his brother’s size. When he suggests his own is a fair comparison, he leaves her with a tempting offer: "Meet me at the watermill tonight if you want to see for yourself." Driven by a curiosity she can’t suppress, Seo-young steps into the shadows of the watermill, stepping into a trap of desire she never saw coming.