When Enola Holmes encounters her friend Lady Cecily hiding behind a peculiar pink fan, she finds it strange and unsettling. Lady Cecily is being held hostage in an abysmal orphanage, coerced into a miserable marriage.

Enola joins forces with her much older, famous brother, Sherlock Holmes, whom she has fought desperately to elude, and risks her own freedom to rescue her friend.

As Enola and Sherlock delve deeper into the mystery, they must navigate the treacherous streets of Victorian London and confront dangerous foes to free Lady Cecily from her dire predicament.