The secret log of a murdered lighthouse keeper falls into the hands of the immensely wealthy Gilbert Frobisher, who discovers encoded within it a stunning and dangerous mystery. Against all odds Langdon St. Ives and his companions set sail in the dark of night for the West Indies aboard Gilbert Frobisher’s steam yacht, pursued by murderous pirates and bound for an uncharted volcanic island on the verge of eruption. There they undertake the perilous search for a hidden treasure protected by an unspeakable pagan god, and in the process unleash a power that will ultimately threaten the devastation of London.