The young lady Mary Jekyll, left an orphan after the death of her mother, was ready to bravely drag out a semi-beggarly existence. However, at a meeting with the family lawyer, Mary is surprised to learn that her mother monthly transferred impressive sums to a shelter for poor girls. Intrigued, Mary travels there and meets 14-year-old Diana Hyde, who claims that she and Mary are sisters. This is how the story of the ladies' club "Athena", incredible adventures and the investigation of the crimes of the secret society of alchemists begins. And Mr. Sherlock Holmes and Dr. Watson will help Miss Jekyll in this difficult matter. However, Mary will help the famous detective unravel a series of bloody murders in Whitechapel and get on the trail of Jack the Ripper.