Summer 1880.
Lipetsk, a spa town in Russia.
The elderly and cantankerous Princess Belskaya suffers a violent reaction while taking a mud bath at the famous Lipetsk Sanatorium. Soon after, she dies.
Dr Roldugin, the medical director of the sanatorium, is at a loss to explain the sudden and shocking death.
He points the finger at Anna Zhdanova, a medical assistant who was supervising the princess’s treatment.
Suspicion also falls on the princess’s nephew Belsky, who appears far from grief-stricken at his aunt’s death.
Meanwhile, investigating magistrate Pavel Pavlovich Virginsky arrives in Lipetsk from St Petersburg, seeking treatment after a nervous breakdown.
Against his better judgement, Virginsky is drawn in to the investigation. But is he getting closer to the truth or walking straight into a deadly trap?