In a world exclusive, Professor Alice Roberts follows a decade-long historical quest to reveal a hidden secret of the famous bluestones of Stonehenge. Using cutting-edge research, a dedicated team of archaeologists led by Prof Mike Parker Pearson have painstakingly compiled the evidence to fill in a 400-year gap in our knowledge of the bluestones — and to show that the original stones of Britain's most iconic monument had a previous life. From the grand fantasy of medieval Merlin legends, to the chemical signatures in microscopic rock fragments, no stone is left unturned in the search for new evidence. By combining innovative 3D scanning techniques, traditional field archaeology and novel laboratory analysis, the team have discovered when and where the stones for Stonehenge were quarried and where they first stood. Alice shows how the team discovered that the stones must have been quarried 400 years before they were first erected at Stonehenge. The team then focuses on trying to find out if the same stones had an earlier life. Alice joins Mike as they put together the final pieces of the puzzle — not just revealing where the stones came from and how they were moved from Wales to England, but also solving one of the toughest challenges that archaeologists face. Their revelations will rewrite the history of Stonehenge forever — this is the story of Stonehenge's lost circle.