Merrick Tremayne is an expeditionary botanist. In 1859, the year of a spectacular solar storm, he is sent to collect specimens of the quinine-yielding cinchona tree, which is to be found only in the Peruvian mountains. Two previous expeditions have disappeared there.

When he arrives at the tiny mission of New Bethlehem, he finds a glass beach and a town built entirely on rock stacks. The townspeople are all crippled, and it seems that their lives are devoted to the ritual production of salt. Superstition abounds; venturing into the forest is forbidden, the strange statues that litter the town must be worshipped, and nobody will discuss the fate of the last expeditionaries. But while Merrick waits for his equipment to arrive by sea, a child goes missing, and along with the missionary, Raphael, he is pulled into a search that takes them deep into the rainforest. Soon, Merrick's scientific mind is at a loss. He cannot tell what makes the wood of the forest trees explosive, or how the statues seem to move - or why Raphael is turning slowly to stone.