Nearly 20 years after the death of Princess Diana, her sons and heirs, Prince William, Duke of Cambridge, and Prince Harry, look back on the life and work of their remarkable mother, and how her influence shaped their lives. Their Royal Highnesses also offer their perspectives on Princess Diana's unique contribution to public life, including her charitable and humanitarian work. The film includes contributions from many key figures in the Princess' life, as well as extensive, never-before-seen personal archive materials.