Adventure in the 1870's with an unusual twist -- a river boat stuck on a treacherous Florida swamp lake -- occurs fantastically but believably in the lives of four children and their aunt. They are riding the small Palmetto Queen, on route from Charleston to a new plantation home, up the Oklawaha River, and have as traveling companions two ineffectual young lawyers, an Italian opera star and her maid and a blustering Captain. When the goes aground in Vanishing Lake, it is the young Renfroes, particularly Randy, 14, and his tomboy sister, Pug, 12, who prove to be the only practical and capable passengers. Their efforts to find help take them into the marshes, Inhabited not only by snakes and cranes but by a wise old hermit, Muskie McGee, who is cooperative, and by untrustworthy hunters, who are not. The singer turns out to be a product of the backwoods, and not an Italian, whose knowledge of Indians and such is most welcome. A bright, humorous episode ends with the Queen safely on her way and all the voyagers better friends. The Florida swamp ""atmushphere"" is effective.