Alan Cumming grew up in the grip of a man who held his family hostage, someone who meted out violence with a frightening ease, who waged a silent war with himself that sometimes spilled over onto everyone around him. That man was Alan's father, Alex Cumming. Alex was the dark, enigmatic heart of Cumming family life. But he was not the only mystery. Alan's maternal grandfather, Tommy Darling, had disappeared to the Far East after the Second World War. The last time Alan's mother saw her father she was eight years old. When she was 13, the family was informed that he had died in an accidental shooting. Curious to explore this second mystery, Alan committed to filming an episode of the BBC's Who Do You Think You Are? Then out of the blue, his father, who Alan and his brother had not seen or spoken to for more than a decade, called. He had a secret he had to share, one that would shock his son to his very core and set in motion a journey that would change Alan's life forever. At times suspenseful, at times deeply moving, but always brave and honest, Not My Father's Son is a powerful story about embracing the best aspects of the past and triumphantly pushing the darkness aside.