They created cinema's greatest love story, but behind the scenes, Humphrey Bogart and Ingrid Bergman could barely stand each other. As Rick and Ilsa, they made millions believe in true love. In reality, one was trapped in a violent marriage, the other hiding secrets that would soon shock the world. Decades later, their co-stars are finally revealing what really happened between takes on Casablanca—and why these two stars never worked together again.