The Lost King of Oz (1925) is the nineteenth of the Oz books created by L. Frank Baum and the fifth written by Ruth Plumly Thompson. It was Illustrated by John R. Neill.
So whatever happened to Pastoria (Ozma's father) - King of Oz in the old days, long before the Wizard came to Oz and erected the Emerald City? That question has been asked many times. Long an Oz mystery, this book settles the matter at last. You won't be surprised to learn that the old witch Mombi (first introduced in The Marvelous Land of Oz) is involved.