Plot
Enola Holmes is the youngest child in the Holmes family, she is extremely intelligent, observant, and insightful. Her mother Eudoria has taught her everything from chess to jujitsu and encouraged her to be strong-willed and independent, to defy the social norms for women of the time.
On her sixteenth birthday, Enola wakes to find that her mother has disappeared, leaving behind only some gifts. A week later, she meets her older brothers Mycroft and Sherlock. Sherlock finds her intelligent, whereas Mycroft finds her troublesome and as her legal guardian, intends to send her away to a finishing school run by Miss Harrison, his old friend.
The flower cards left by her mother reveal secret messages and lead to hidden money, which Enola uses to escape, disguised as a boy. On the train, she finds the young Viscount Tewkesbury hidden in a travel bag. Enola thinks he is a nincompoop, but warns him that a man in a brown bowler hat named Linthorn is on the train searching for him. Linthorn finds and tries to kill Tewkesbury, who escapes with Enola by jumping off the train. He forages for edible plants and fungi, they return to London and part ways.
Dressed as a Victorian lady, Enola continues to trace Eudoria, leaving cryptic messages in the newspaper personal advertisements. Enola discovers pamphlets and a safehouse containing explosives, and learns that Eudoria is part of a radical group of suffragettes. She is attacked by Linthorn, who interrogates her about Tewkesbury, then attempts to kill her. Enola fights back, ignites the explosives in the safehouse and escapes.
Enola decides to find Tewkesbury again, to save him from Linthorn. She visits the Tewkesbury estate, where she meets Tewkesbury's grandmother, the Dowager. Mycroft has Inspector Lestrade of Scotland Yard search for Enola Holmes.
Enola finds Tewkesbury selling flowers in Covent Garden and warns him of Linthorn. Taking him to her lodgings, she is caught by Lestrade, and Mycroft forces her to go to Miss Harrison's finishing school. Sherlock visits Enola and admits he is impressed by her detective work. Tewkesbury sneaks into the school and they escape together, stealing Miss Harrison's motor car. Enola decides they must go to Basilwether Hall and face Tewkesbury's uncle, who she has deduced was trying to kill him.
The estate is seemingly deserted, but Linthorn ambushes them. Enola trips him using jujitsu, causing a fatal head injury. Tewkesbury's grandmother is revealed to have hired Linthorn. As a staunch traditionalist, she did not want Tewkesbury to take his father's place in the House of Lords and vote for the Reform Bill. She shoots him, but he survives, having hidden a plate of armor under his clothes. Sherlock arrives at Scotland Yard, where Lestrade informs him of Enola's actions as they plan to have the Dowager arrested.
Enola shares a tearful goodbye with Tewkesbury. She eavesdrops on a meeting between Sherlock and Mycroft, where Sherlock suggests becoming her guardian. Upon returning to her lodgings, Enola finds Eudoria waiting there. She explains why she had to leave, and why she must leave again, but she is impressed by what Enola has become. Enola has found her purpose—she is a detective and a finder of lost souls.
