(Note: This interview first aired last November.) Our guest is David Grann, a staff writer at The New Yorker Magazine. He's the bestselling author of "The Lost City of Z," "Killers of the Flower Moon," "The Old Man and the Gun," and other books. Grann joins us to discuss his newest work of nonfiction, "The White Darkness," which profiles one Henry Worsley, a family man and decorated British special forces officer who also happened to be obsessed with Ernest Shackleton, the 19th-century polar