On board the moletrain Medes, Sham Yes ap Soorap watches in awe as he witnesses his first moldywarpe hunt: the giant mole bursting from the earth, the harpoonists targeting their prey, the battle resulting in one's death & the other's glory. But no matter how spectacular it is, Sham can't shake the sense that there is more to life than traveling the endless rails of the railsea--even if his captain can think only of the hunt for the ivory-colored mole she's been chasing since it took her arm all those years ago. When they come across a wrecked train, at first it's a welcome distraction. But what Sham finds in the derelict--a kind of treasure map indicating a mythical place untouched by iron rails--leads to considerably more than he'd bargained for. Soon he's hunted on all sides, by pirates, trainsfolk, monsters, & salvage-scrabblers. & it might not be just Sham's life that's about to change. It could be the whole of the railsea.