The mystery at the old mill is a deep-rooted secret that haunts the Hersel family. While most of the family would like to forget the past, two cousins have turned the decades-old mystery into a treasure hunt. Originally designed to be a children's game, the pursuit of fortune soon becomes an obsession, but not just for the two cousins. When the relatives gather to celebrate Aunt Bert's 80th birthday, the old mystery quickly resurfaces. The family is forced to come to terms with the mystery and a murder. Marshall Edmonds returns to help his son sort through the Hersel past. However, first Marshall must solve the mystery at the old mill and he will soon discover that the past and the present have a lot in common