On board the moletrain Medes, Sham Yes ap Soorap witnesses his first moldywarpe hunt. The battle between giant mole and harpoonist is extraordinary. But no matter how fascinating it is, Sham cannot shake the sense that there is more to life than travelling the endless rails of the railsea. When they come across a wrecked train, it is a welcome distraction. But the impossible salvation Sham finds in the derelict leads to more than he'd bargained for. Soon he's targeted on all sides, in a hunt that could change not only Sham's life, but the whole of the railsea.