In the early sixties two national treasures were the creative force behind one of British cinema's most successful franchises. But there's an intriguing mystery behind the Miss Marple movies. They were almost never made... Agatha Christie didn't want Margaret Rutherford to bring her most cherished creation to life. And Margaret Rutherford was mortified at the prospects of sullying her reputation with something as sordid as murder... This is the story of the real reason why the acting legend and "funniest woman alive" didn't want to take on the role that made her celebrated across the world. Margaret and Agatha form an unlikely friendship filled with afternoon tea, brandy snaps and gossip. Meanwhile Agatha turns detective herself and she's on a mission. She's determined to unearth Rutherford's tragic and shocking secret.