Lydia Douglas had long dreamed of starting her own business, and it had to happen that difficulties arose with her first client - Alexey Roshchin hires a girl to compile his family tree. He is interested in the history of the Roshchin family, and specifically in the person of his great-great-grandmother Irina, from whom she left a pocket Bible, a small old key that opened no one knows what, and a beautiful love story with Alexei Roshchin, who later became her husband. But Irina’s happiness did not last long; her husband was killed because of one insidious person. And now Alexey Roshchin from the 21st century asks Lydia to sort out old family secrets. The golden key will help her with this. It was kept in the Roshchin family for several centuries and, according to legend, is capable of opening any door and learning any secrets...