Who is Lizzie Pinter from A Test of Wills and what is their importance?

Lizzie Pinter is a very young girl who happens to be out picking flowers in the meadow on the morning of the murder. Believing that the gory, headless man on the horse is her beloved father, Lizzie withdraws into her mind, refusing to eat or sleep or speak. It takes Ian Rutledge finding the little girl's doll, and showing her some insightful compassion to make her realize that her dear Papa is alive. She did not witness the murder, however, only the aftermath.