Fast-forward to the future
(Book)

This time a strange flashing cube from the magic suitcase sends them to a nearby city, Hadenstown, in the future, and they find themselves surrounded by flying cars, tall glass buildings, and robots; but Randall is also there, and the two children must scramble to figure out just what the mysterious cube is and get it back where it belongs--and their quest brings Chase face-to-face with his future self, Professor Teslar.