TRAINing day! Batman and The Joker's ability to function as a team is put to the biggest test yet as they are dropped out of the sky and into a moving train! Will their alliance hold together, even if the speeding locomotive does not? Meanwhile, the Dark Knight has enlisted the help of Nightwing and Catwoman to help with his investigation, but with more pieces of Gordon being shipped to GCPD headquarters, by the time they find any clues, will there even be enough of the commissioner left to save?