Mr. Edison has just invented a long-burning light bulb, but he's keeping a huge secret: he's also discovered time travel. In fact, he built his own time machine. The kids get an even bigger surprise when a young Mr. Crowe walks into Edison's laboratory - as his assistant! The older and dangerous Mr. Crowe is sneaking around Menlo Park, too, with plans to destroy the time machine. If he does, George and Gracie will be stuck in 1879...forever. The twins need Mr. Edison's help. But can they stop Crowe in time?
George and Gracie begin their adventure in Dover, Delaware 1776. The kids are surprised to discover that one of them changes into an animal every time they travel, and this time Gracie is a horse. All the twins want to do is return a pair of antique school desks and search for their parents. But instead they find themselves in the middle of the American Revolution and end up helping Caesar Rodney make his famous ride into Philadelphia to vote “yes” for the Declaration of Independence. Crowe lands in Delaware, too, and he plans to take the time machine - with George and Gracie inside!
In this next adventure, George and Gracie travel back in time to Hershey, Pennsylvania, in 1907. Their mission: To return an antique rug and rescue their parents. When the time machine lands them smack-dab in the middle of a barn, George turns into…something pretty weird. And Gracie drives a car into a fence. They meet Milton Hershey, the chocolate king, who invites them to be his chocolate tasters. But when George and Gracie discover a plot to steal Mr. Hershey's perfect - and secret - chocolate recipe, they put themselves in danger to stop the thieves.