With no clients, Enola Holmes (Millie Bobby Brown) plans to close her detective agency. Then, match-girl Bessie Chapman (Serrana Su-Ling Bliss) asks Enola to find her sister, Sarah Chapman (Hannah Dodd). They work at a match factory where deaths are blamed on typhus. At the factory, Enola and Bessie meet Mae (Abbie Hern).

Enola trails Mae to the Paragon Theatre where Sarah and Mae dance. Enola discovers a poem for Sarah from a secret lover.

Meanwhile, Sherlock (Henry Cavill) can’t track the money involving the blackmail of government officials.

Enola discovers a code in the poem mentioning a house in Whitechapel. Mae is in the house, stabbed and dying with sheet music hidden in her dress. Superintendent Grail (David Thewlis) accuses Enola of murder. She runs to Sherlock’s flat.

At a ball held by the Lyon family, the match factory owner, Enola talks to Cicely and Mira Troy (Sharon Duncan-Brewster -Brewster), secretary to Treasury Minister Lord Charles McIntyre (Tim McMullan).
Sherlock figures out Moriarty is the blackmailer.

Grail arrests Enola. Eudoria (Helena Bonham Carter) and Edith (Susie Wokoma) free her. Enola realizes Cicely is Sarah Chapman, and that Sarah, Mae, and William Lyon (Gabriel Tierney), son of the factory owner, learned the factory deaths were from cheap phosphorus from a deal between McIntyre and William’s father.

Enola meets Sherlock at the factory. At the theatre, they discover evidence using a map on the sheet music. Sarah confirms everything. Grail and the police arrive, but Grail is killed. McIntyre enters, burns the evidence, and tries to get Sarah arrested. Sherlock and Enola realize Mira Troy is Moriarty. McIntyre and Moriarty are arrested, but Moriarty escapes.

Sarah, Bessie, and Enola organized a matchgirls’ strike honoring labor activist Sarah Chapman who organized the 1888 matchgirls' strike. Watch on Netflix.