Barely making it to Mars in their crippled aether cutter, Nathanial and Annabelle crash in the desolate Martian wastes. A disfigured Martian with a mysterious past helps them survive in the desert, but when they are rescued by a passing caravan their troubles may only have started. Raids by steppe nomads and flying skrill riders are the most obvious dangers, but simmering resentment against Earth humans, and intricate plots to overthrow the British colony, lurk everywhere just beneath the surface. Apparent friends become enemies, unexpected allies appear from unlikely sources, and the shadowy past of their Martian guardian collides with the sinister plans of the murderous head of the dreaded Martian Cult of the Worm...