The wizard of Menlo Park, New Jersey

"During the coldest winter ever, George and Gracie land in Menlo Park, New Jersey, 1879--near Thomas Edison's famous laboratory. Mr. Edison has just invented a long-burning light bulb, but he's keeping a huge secret: he's also discovered time travel. The twins need Mr. Edison's help to protect the time machine from Crow. But will they stop Crowe in time?"--Back cover.