Hosted by Jane Pauley. In our cover story, Susan Spencer looks at the hopes and concerns surrounding a new drug for Alzheimer's Disease. Plus: We look at the legacy of Broadway's Stephen Sondheim, including a conversation between the composer and Tony-winning actress Patti LuPone; Jim Axelrod interviews Pat Benatar and her husband, guitarist Neil Giraldo; Ben Mankiewicz profiles "Cagney & Lacey" star Sharon Gless; Conor Knighton explores the oldest trees in the world; David Pogue offers an explanation of inflation; and Kelefa Sanneh talks with the host of HBO's "How To with John Wilson," whose pseudo instructional videos capture New Yorkers at their most unguarded.