The Pitch: Herman J. Mankiewicz (Gary Oldman) was the script whisperer of the 1930s — at the height of the studio system, he was one of its most sought-after names, punching up many of the era’s most famous films with his signature wit and effortlessly fast-paced dialogue. But he was also a man plagued by personal foibles, a hefty drinking problem, and the struggles of being a card-carrying socialist in one of the most capitalistic industries in American history. In the spring of 1940, Mankiewicz — but please call him “Mank” — was tapped to pen the script for Hollywood’s most famous piece of outsider art: Orson Welles’ sprawling, ambitious epic Citizen Kane. Recovering from a car crash in a private estate with a helpful nurse named Rita (Lily Collins) and a 90-day deadline to get...