When Ben Cartwright returns to his family home to mourn his father's death, he unexpectedly discovers a series of cryptic letters between Arthur Conan Doyle and his great-great-grandfather, who mysteriously disappeared during a jungle expedition in the Amazon in 1908. This correspondence leads to the incredible conclusion that his ancestor's expeditions served as the basis for the famous author's fantastic story about a forgotten world full of prehistoric creatures. Ben conducts his own investigation and learns of a lost notebook that supposedly contains a map of this place. But he is not the only one searching for this map—after all, the existence of such a place could challenge everything modern science has taught us. Together with a group of friends, Ben embarks on a dangerous journey.