Tintonia

Four children (Samuel, Thomas, Georgie and Rebecca) enter a world called Tintonia that exists under the ground in another dimension. They are befriended by the Elfin people and receive help and special gifts from the different characters that they meet, including a Mermaid named Narda, a Giant called Robert and a Wizard called Dr Hitzvelgar. They learn to stick together and eventually return to their own world, having helped to defeat an army of Dwarfs. This story perfectly combines the adventures of The Famous Five with the fantasy world of Alice in Wonderland.