In the spring of 2011, when he got word that he was being fired as president and chief operating officer of Warner Bros. Pictures, Alan Horn was blindsided. He was 68, and while no one said it explicitly, the message was made clear: Time Warner C.E.O. Jeff Bewkes wanted to make room for younger blood.

In the weeks following his dismissal, as Horn flew back and forth from Los Angeles to New Zealand, where he was serving as the executive producer on Peter Jackson’s The Hobbit: An Unexpected Journey, he tried to talk himself out of the crevasse he felt opening beneath him. “He was so depressed,” says the director Rob Reiner. “He had that insecurity that actors have: I’ll never work again!” Horn had had a breathtaking run. For 7 of his 12 years as head of Warner Bros., the studio led the global box office, knocking out hits such as the eight Harry Potter films, the Ocean’s Eleven series, the second and third Matrix movies, and The Departed. He had plenty of money, a house in Bel Air rigged out with a collection of Western art, a long and happy marriage to climate activist Cindy Horn, two well-adjusted daughters, and a disarming reputation as one of the nicest guys in Hollywood.