Comedian Lee Mack was born Lee McKillop in the north of England, just like his McKillop great-grandfather, who was also a comedian, known as Billy Mac. Lee has a few playbills from Billy Mac's variety hall performances, but knows little more about him. Not long into his journey, Lee discovers that his great-grandfather was passionate about more than making people laugh. Billy Mac joined the first ever pals battalion in Liverpool at the start of the First World War and honed his act at the front lines in the Battle of the Somme.

Lee is also curious about his maternal grandad Joe's upbringing - deserted by his unwed mother and raised by his grandparents in County Mayo at the time of the Irish Civil War.

Strictly Come Dancing's head judge Shirley Ballas investigates a family story that her maternal great-grandmother abandoned her husband and children for a more exciting life in America. What Shirley discovers casts her great-grandmother in a completely new light.

On her father's side, Shirley pursues a rumour that she has black ancestors - a trail which leads her to colonial Cape Town and the era of slave trafficking to South Africa via the Indian Ocean.