The Twist of a Knife

This is the fourth installment in a series featuring a fictionalized version of author Anthony Horowitz and his reluctant partnership with Daniel Hawthorne, a private detective. Anthony visits Hawthorne's flat near Blackfriars Bridge to end their arrangement, citing Hawthorne's secrecy, the dangers he has endured, and his subordinate role. Hawthorne pushes back, revealing he has signed with Anthony's literary agent, Hilda Starke. Anthony refuses to continue but invites Hawthorne to the opening night of his play, Mindgame, at the Vaudeville Theatre. Hawthorne declines.

Mindgame is a comedy thriller set in a psychiatric asylum, featuring trick set design where doors and furniture secretly change to mirror the theme that nothing is as it seems. Producer Ahmet Yurdakul and his devoted assistant Maureen Bates have brought the play to the West End after a successful regional tour. The cast includes Jordan Williams, a Lakota method actor; Sky Palmer, a guarded young actress; and Tirian Kirke, a rising star who joined for the London run. The director, Ewan Lloyd, carries the burden of a past production of Saint Joan at Chichester, where a fire severely injured the lead actress, Sonja Childs.

On opening night, the performance goes well, but at the cast party the influential Sunday Times critic Harriet Throsby appears unexpectedly with her daughter, Olivia. Critics never attend such parties, and Harriet's barbed comments unsettle everyone. She overhears Tirian disparaging the director of his upcoming film, Tenet, and gives him a look of malevolence.

Back in the theatre's green room at midnight, Sky reads Harriet's review aloud. It is savage, attacking every aspect of the production by name. Jordan erupts, declaring he wants to kill Harriet and stabbing an ornamental dagger into a cake. These daggers, leftovers from Ahmet's previous Macbeth production, were given as first-night gifts. Anthony notices the medallion on his own dagger is loose. The party collapses, and Anthony walks home without remembering what he did with his dagger.

The next afternoon, Detective Inspector Cara Grunshaw and Detective Constable Derek Mills inform Anthony that Harriet was stabbed to death in her Little Venice home around ten o'clock that morning. The murder weapon matches Anthony's dagger, the only one with a loose medallion. His fingerprints are on it, a hair matching Anthony's was found on the body, and a CCTV image places a man resembling him near the scene. He has no alibi. Grunshaw, who holds a grudge from a previous case, arrests him.

After a night in custody, a computer problem at the forensic laboratory delays the DNA results, and Anthony is released. Hawthorne, waiting outside, reveals that Kevin Chakraborty, a teenage hacker who lives in his building and has Duchenne muscular dystrophy, launched a cyberattack on the lab's servers to buy them time. Kevin confirms the DNA is a match. Hawthorne estimates they have 48 hours before Grunshaw rearrests Anthony.

They visit Harriet's husband, Arthur Throsby, a history teacher. In Harriet's study, three true-crime books include Bad Boys: Life and Death in an English Village, about two boys involved in a teacher's death in Moxham Heath, Wiltshire. When Olivia arrives, she expresses hatred for her mother and accuses Anthony of threatening Harriet at the party.

Returning to the Vaudeville, Hawthorne finds a crumpled packet of Ahmet's cigarettes in the green room dustbin. Anthony realizes his dagger was taken from this room, meaning someone framed him. They interview the cast before the evening performance. Jordan denies killing Harriet but claims Anthony agreed with his threat. Tirian describes a childhood of orphanhood; Anthony catches him in a lie about refusing a role in Anthony's TV show Injustice. Sky, secretly in a romantic relationship with Olivia that the two kept hidden because Harriet held anti-gay views, reveals that Olivia sent her the review by accessing Harriet's computer. Sky also claims Anthony showed her a magazine containing Harriet's address, which he does not remember.

They visit Ahmet, who reveals his company is going bankrupt, and Ewan, who describes Harriet's coded taunts about fire at the party and mentions a strange chill at the back of his neck as he left the green room. When Ewan's wife arrives, Anthony is shocked to discover she is Sonja Childs. That evening, Jordan confronts Anthony near his flat, initially objecting to Anthony's portrayal of his Indigenous heritage but relenting after learning about the arrest. Jordan shares that Tirian was terrified Harriet would publicize his remarks about Tenet and destroy his career.

They visit Martin Longhurst, Ahmet's accountant, who reveals he is the brother of Stephen Longhurst, one of the two boys convicted for the death of Major Philip Alden at Moxham Heath. Harriet's book destroyed his family. In Wiltshire, a groundskeeper contradicts Harriet's account, insisting Stephen dominated the other boy, Wayne Howard, not the reverse. Major Alden's widow admits the Longhursts' lawyers bribed her to testify that Wayne was the ringleader, resulting in Wayne receiving ten years to Stephen's five. In Bristol, a retired editor suggests Harriet may have poisoned a colleague to take over his position as drama critic.

The forensic lab comes back online, and police arrive at Anthony's flat. He flees to Hawthorne's flat. The next morning, Hawthorne's adoptive brother Roland visits, and Anthony learns Hawthorne was adopted after his birth parents died. Hawthorne returns, says he has solved the case, and brings Anthony to the Vaudeville, where all suspects are assembled onstage and Grunshaw waits in the stalls.

Hawthorne reveals that the killer intended to frame Jordan, not Anthony. The killer took a hair from a towel in Jordan's dressing room, not knowing Anthony had dried his hair with it, and grabbed the wrong dagger. To access the green room after hours, the killer broke a backstage light bulb as a diversion, wedged the fire exit open with the crumpled cigarette packet, and returned later to collect the hair and the weapon. Ewan's mysterious chill was simply a draft from the propped-open door.

Hawthorne identifies Tirian as the killer and reveals his true identity: Wayne Howard, the boy convicted for Major Alden's death. After his release, Wayne received a new identity through Multi-Agency Public Protection (MAPP), a government program for managing offenders. He chose his stage name from characters in the C.S. Lewis Narnia books, which his childhood friend Stephen had loved. His biography was fabricated by the probation service, which also forbade him from taking the Injustice role because playing a young offender could have exposed his past. Harriet recognized Wayne at the party and embedded coded signals in her review, calling his performance "childish" and noting she "recognised" him. Terrified she would expose his identity, Wayne killed her. Tirian does not deny the accusation and is arrested.

Weeks later, Hawthorne presents Anthony with a contract for four more books, noting that if Anthony declines, he will bill him thousands for his detective work. Recognizing that Hawthorne saved his freedom and his career, Anthony picks up a pen and signs.