It’s the roaring 20s, and a young flapper named Lorelei decides to keep a diary after receiving a blank journal from a “gentleman friend.” She has an apartment in New York paid for by a Chicago businessman named Gus Eisman; when he’s in town, Mr. Eisman spends his time “educating” Lorelei by going out to dinner, taking in shows, and then escorting her to her apartment to “talk about the...