Under the Mountain - Full Series

Episode One - Maar
In the prologue, young twins Theo and Rachel get lost in the bush. While search parties try to find them before it's too late, the mysterious Mr Jones (Roy Leywood) enters the fray. Years later, the twins come to stay with their aunt and uncle in Takapuna, and Rachel thinks she has seen Mr Jones again. The twins spy a strange man at a ramshackle old house nearby. That night, something slimy stirs outside Rachel's room. 

Episode Two - Volcano of the Bleeding Skies
Rachel (Kirsty Wilkinson) and Theo (Lance Warren) catch another glimpse of the mysterious man — Mr Wilberforce. Then they visit Mount Eden with their cousin Ricky (Bill Ewens) and Aunt Noeline (Glynis McNicholl). In the volcanic crater, eerie voices echo in their heads, and the voice of Mr Jones (Roy Leywood) warns them to get out. Later, he tells them to avoid the lake and the sea — but Ricky is all set to take them on a boat trip to Rangitoto.

Episode Three - Red Force, Blue Force
While jetboating back to Takapuna from Rangitoto Island, Ricky and the twins find themselves battling a strange creature. Back on shore, they make a bizarre discovery in the back of the Wilberforce's car. The twins finally have a proper conversation with Mr Jones, who shows them how to communicate telepathically, and tells them they have "special qualities" because they're bonded. But then he does something to their memories.  

Episode Four - The Alien World Below
Rachel is awoken by voices — Mr Jones is pleading for help. She and Theo paddle across to the Wilberforce house in the dead of night, in time to glimpse strange creatures heading toward the water. Inside, they find a model of the universe and a stairway. Soon, they find themselves trapped. Their only means of escape is sliding down into another world.

Episode Five - Weapons of the Mind 
Rachel and Theo find themselves in a vast series of caverns and tunnels beneath Auckland. But they're not alone. After managing to make their escape, they head to Mount Eden with Mr Jones, who finally reveals the story of the alien creatures. 

Episode Six - Any Shape, Any Form
Mr Jones tells the twins about past encounters with the aliens, and explains how the twins can use two powerful stones to defeat them. But the aliens are closing in. They attack Mr Jones and arrive in disguise when the twins are alone. The next morning, strange doings are afoot.

Episode Seven - Assault
Time is running out: soon, the aliens will be free. Preparations begin for the twins to save the day. After going into hiding with Mr Jones, they continue trying to master the stones — Theo's questioning nature proves a barrier rather than an advantage. With Ricky's help, the trio manages to make it back to Rangitoto for a final confrontation.

Episode Eight - The Gift of Oblivion
As time runs out for the twins to save the day, Theo has a difference of opinion with Mr Jones. The Wilberforces are on Rangitoto Island, and out on the hunt. The twins and Mr Jones head back into the tunnels, though Mr Jones soon teleports back to Rangitoto, where tragedy strikes. On Mount Eden, Theo faces the aliens in a final battle for survival.