The second in the five-book series, The El Dorado Adventure continues the exciting experiences of Miss Vesper Holly, daughter of deceased anthropologist Benjamin Rittenhouse Holly. Narrated by Vesper's guardian Brinnie, the plot involves Vesper and Brinnie's trip to El Dorado, where the two encounter Dr. Helvitius, their adversary in The Illyrian Adventure. As in the previous book, Vesper must foil the schemes of Helvitius, who now plans to exploit the Chirican Indians by taking their land and destroying their heritage. During the course of the adventure, Vesper and Brinnie make friends with an assortment of unusual characters and become involved with the Chiricans and their problems. Brinnie is deceived by the surface appearance of one handsome young man, while Vesper is attracted to another. The book ends with good triumphing over evil, although as usual, Dr. Helvitius escapes to scheme for later adventures.