As an adventurer, wilderness expert and chief scout, Bear Grylls has travelled to some of the most hostile environments in the world, sharing his survival secrets with audiences of millions. Bear is curious about a tendency to ‘follow the path less trodden' so he's now embarking on a journey into his family's history. The trail starts at home where, alongside his wife Shara, Bear explores his paternal grandfather Ted Grylls's old trunk, intriguingly full of documents marked ‘Top Secret'!Bear heads to Sandhurst Military Academy where his grandfather Ted trained to be an army officer in the 1920s. Here Bear discovers Ted's fascination with all things mechanical – especially tanks. With help from the team at the British Tank Museum, Bear learns how Ted became one of the British Army's biggest experts in armoured vehicles and tank warfare, advising both the British and Americans on how to win on the battlefield and contributing to the success of the D-Day landings.But it's Ted's job leading top secret organisation T-Force that helps Bear really understand the pressures his grandfather faced and reveal clues about his character. Charged with identifying, tracing and sometimes even kidnapping Germany's best scientists for interrogation by the Allies after the war, Ted had to stay in Europe long after World War II was over, working on a morally complex mission, far from his family.Bear also wants to find out more about the life of his beloved, ‘bear hug of a man', grandad Neville. Neville's father and Bear's great-grandfather, Lionel Ford, is revealed to be a loving family man and progressive headmaster who modernised Harrow School. In Harrow's Headmaster's House, where his grandad played as a boy, Bear discovers the truth behind a family tragedy – the death of his great uncle Richard, who died of an infection as a teenager. As a father of three boys himself, Bear is moved to read Lionel's own words about his grief and love for a lost son.Finally, following his family line back several centuries reveals, to Bear's delight, Scottish ancestry. His habit of walking the dog in a kilt no longer feels fraudulent! A trip to Scotland uncovers the story of Bear's ten-times great-grandfather the Duke of Argyll, whose religious beliefs and devotion to Scotland cost him his head, courtesy of the Scottish maiden, a gruesome type of guillotine. And at his last destination, his mum's dreams of a royal connection come true. At the Argyll Mausoleum, Bear discovers his 21-times great-grandfather is none other than a famous Scottish king.