Our ponderous pachyderm friends of Celesteville, King Babar and Queen Celeste, are visited by the Old Lady and her brother Professor Grifaton -- a typical butterfly collector, with his two children Colin and Nadine. Nadine discovers a cave which the children (elephant and human) use for a playhouse. They hold a costume ball. Alexander -- the elephant's child -- falls down a tunnel in the cave. Professor Grifaton investigates and finds it's an underground river with an agrees into the Celesteville lake. The chance investigation initiates an excursion steamer to visit the caves. (There are bizarre pictures of the mammoth elephants in ministure rowboats gazing at stalagmites.) Story is strong, the pictures are smashing as ever. . . but the stitching is weak.