"It is said in those districts that not all the trains which run on the city’s tracks are listed in Metropolitan Transit’s compendious schedule. The residents will tell you that after midnight, on some nights, there will be other trains, trains whose cry is different, the bellow of some great beast fighting for its life. And if you watch those trains go past, behind those bright flickering windows you will see passengers unlike any passengers you have seen when riding the trains yourself: men with wings, women with horns, beast-headed children, fauns and dryads and green-skinned people more beautiful than words can describe. In 1893, a schoolteacher swore that she saw a unicorn; in 1934, a murderer turned himself into the police, weeping, saying that he saw his victims staring at him from a train as it howled past the station platform on which he stood.
These are the seraphic trains. The stories say they run to Heaven, Hell, and Faërie. They are omens, but no one can agree on what they portend. And although you will never meet anyone who has seen or experienced it, there are persistent rumors, unkillable rumors, that sometimes, maybe once a century, maybe twice, a seraphic train will stop in its baying progress and open its doors for a mortal.
Those who know the story of Thomas the Rhymer—and even some who don’t—insist that all these people, blest or damned as they may be, must be poets."
Sarah Monette, Somewhere Beneath Those Waves