Fields of Iron begins rather slowly for one of the Magnificent Devices books, but this is mostly because all our characters ended up somewhat wrecked at the end of Fields of Air. Gloria was stranded with Las Brujas – the witches who inhabit the canyons of the Rio Sangre de Colorado de Christo – while Evan was a prisoner of war with the Californios.Not to worry, however. The action picks back up quickly enough. Evan is forced to operate El Gigante – the mechanical behemoth he has managed to pilot all the way from Resolution to build a dam on the river, working with one of his cellmates to run the mechanical monster. As he gets to know his other cellmates during their few off hours, he finds out that one of them is an unfortunate German or Dutchman who has suffered a major loss of memory, and the other is Barnaby Hayes, the man who kidnapped Gloria during their adventure in Venice. They begin to make plans to destroy the dam and escape. And to rescue Alice when they find that the Californios have shot down her airship on their border.Meanwhile, Gloria, still wishing to stop the war, marries Las Brujas friend, riverboat Captain Stan Fremont as the only way to respectable travel into the Californias, even though it is really Evan that she loves. They are able to meet with the Viceroy. And at the Rancho where they encounter him, they also find Evan and Joe, diverted from their escape and rescue plan to interpret the nightmares the Viceroy has been having. But the Viceroy himself manages to surprise them.