Rosie gets an amazing postcard from her Great-aunt Rosamund in Africa, and she can't wait to look up a map of Kenya and find out exactly where it is. On the shelves of the old castle library, however, she finds more than just the atlas she was looking for. Hidden behind the book is a beautifully carved wooden statue that turns out to be another of the Little Princesses her Great-aunt told her about. Before she knows it, Rosie is off to see Africa for herself!

Princess Imena happily welcomes Rosie into her home, and explains that she is a special princess, with the power to bring rain to her people. Mysteriously, however, her magic dance is no longer working and if the river does not begin to flow again soon, she and her family may be forced to leave. Rosie can't resist offering to help her new friend, and soon the girls are investigating black magic and the sinister village witch doctor. Can they bring the river Iku back and save the village . . .?