Batman / Teenage Mutant Ninja Turtles #1

Batman tracks down the Turtles, assuming them a threat, but they have accidentally entered his universe, where conditions will rapidly strip them of their intelligence. Shredder too enters Batman's world and quickly places himself at the head of Gotham's criminals, only to have Ra's al Ghul force himself into partnership. Batman, Splinter, Damian and the Turtles win the day, while Casey and April open a way of return to the Turtleverse.