Abacus

Twelve-year-old AP is crazy about science but Kate, his older sister, has no time for him or his geeky experiments. All that changes when a curious abacus transports them back to Arthurian England. There, AP uses his knowledge to help them out of trouble. On a second adventure, they join the Sioux in Montana and witness CusterвЂTMs defeat at the Battle of the Little Bighorn. Then, in ancient Egypt, AP uses science again, allowing Kate—mistaken for a priestess—to perform вЂ