In the lush landscape of Snowdonia is the ancient cave entrance to an undocumented gold mine from Roman times, hikers searching for shelter from a storm find mutilated bodies and old skeletons on the cave floor. Detective Wallon investigates the cave scene and uncovers the plans used by a cunning businessman for his fraudulent scheme to cheat investors out of their money and share in the gold. Intertwined in the story is Wallon's whirlwind romance with the beautiful Joanna Whitecoft who is accused of murder.