"Parnassus on Wheels" tells the tale of a traveling book-selling business owned by Roger Mifflin. Helen McGill is a 39 year-old woman, working at a farm, who is tired of taking care of her older brother, Andrew. Andrew is a former businessman turned farmer, turned author. As an author, he begins using the farm as his Muse rather than a livelihood. When Mifflin shows up with his traveling bookstore, Helen buys it—partly to prevent Andrew from buying it—and partly to treat herself to a long-overdue adventure of her own. "The Haunted Bookshop" is a suspenseful novel set in Brooklyn around the time of the end of World War I. It continues the story of Roger Mifflin, the book seller in Parnassus on Wheels. A young advertising man, Aubrey Gilbert, stops by a bookstore named "The Haunted Bookshop" in the hopes of finding a new client and meets the proprietor, Roger Mifflin. Gilbert is intrigued by the fact that his firm's biggest client, Mr. Chapman, has asked Mifflin to undertake the education of his daughter, Titania Chapman. Gilbert meets Titania and falls in love with her. Meanwhile, mysterious things start to happen: Gilbert is attacked as he travels home and a pharmacist neighbor of Mifflin is observed skulking in the alley behind the bookstore at night speaking to someone in German. Gilbert suspects that the gregarious Mifflin is involved in a plot to kidnap Titania, and he assigns himself the job of protecting her.