Enola Holmes—international bestselling and Netflix streaming sensation—returns when the rescue of a young woman sends her into battle with her brother Sherlock against his most deadly, implacable enemy—Professor Moriarty.

In February 1891, London, Enola Holmes—the much younger sister of Sherlock and Mycroft Holmes—is attending the burial of her former landlady when she hears the faint sound of a hand-bellim the graveyard. Investigating further, as is the Holmes' family instinct, she discovers that the bell is attached to the temporary tombstone at a recent gravesite and someone, buried within, is pulling the string to ring the alarm. Galvanized into action, Enola and her companions successfully unearth the coffin within, freeing a still-living young woman, Trevonia Trairom. Enola, by predilection and by trade a Scientific Perditorian, a finder of lost things, finds herself comforting and protecting this young girl, who remembers very little, including her own identity. While protecting this mysterious girl from an enigmatic enemy, she finds Sherlock engaged in a related mystery and joins him in his battle against the Napoleon of Crime, Professor Moriarty. As that epic conflict rushes towards its inevitable conclusion, Enola takes her place more fully than ever before as a proud member of the Holmes family.