As luck would have it, Alice Hastings arrives and it seems she may be Jonas Lytton's salvation. Alice is a wealthy patron who hires Lytton to find her missing husband Casper, who disappeared while on a gold-hunting expedition in New Zealand. While Jonas is at first hesitant to accept the venture, he eventually reconsiders and accompanies Alice and his uncle on their journey. They are soon joined by McNiff, a somewhat unsavory character whose knowledge of the Maori culture and language prove him to be indispensable to their expedition. During their adventure, the group finds themselves barely escaping death after they fall into the clutches of a cannibalistic Maori gang. They continue onward and travel inside the mysterious caves of a volcanic crater. Facing death at every turn, they soon arrive at a mysterious underground beach that turns out to be the center of the Earth. Inside, they find evidence that Casper has also been to this uncharted land. But where is Casper?