When Chris Chibnall sat down to adapt Agatha Christie’s The Seven Dials Mystery for Netflix, he was not interested in creating a simple copy. The new three-part series, which launched on January 15, 2026, features a major twist not found in the original 1929 novel. In a recent interview, Chibnall explained his decision to expand the story, stating he wanted to add another layer to the beloved mystery.
The writer, famous for creating Broadchurch, is a lifelong Christie fan. He described rediscovering The Seven Dials Mystery as an adult and being struck by its modern and funny tone. This fresh look inspired him to build upon the foundation of Christie’s work for a contemporary audience.
“I just wanted another layer,” Chibnall said, discussing his approach to the adaptation. “The book has all the things you love in an Agatha Christie novel, but it has loads more, and it has things you might not expect”.
The Biggest Change from Book to Screen
The most significant change in Agatha Christie’s Seven Dials is the identity of the story’s secret mastermind. In Christie’s original novel, the plot to steal a valuable industrial formula is carried out by a group of lower-level conspirators. The Netflix series introduces a new, heartbreaking twist that places the ultimate blame much closer to home for the heroine, Lady Eileen “Bundle” Brent.
Warning: Major spoilers for Agatha Christie’s Seven Dials follow.
In the series, the final criminal is revealed to be Lady Caterham, Bundle’s own mother, played by Helena Bonham Carter. This character is a gender-swapped version of the book’s Lord Caterham, who is a harmless and uninvolved figure in the original story. The adaptation transforms her into a figure twisted by grief and financial desperation, orchestrating the theft that leads to multiple murders.
“It was you all along,” Bundle tells her mother in a climactic scene on a train. Lady Caterham planned the party that kicks off the series to gather intelligence.
This change fundamentally alters the story’s emotional core. It turns the mystery into a deeply personal betrayal for Bundle, who discovers the person she should trust most in the world is responsible for the chaos and death around her.
Exploring Grief in a Post-War World
Chibnall and the creative team used this new character direction to explore deeper themes. The series is set in 1925, a period shadowed by the losses of World War I. The trauma of that conflict is a driving force for many characters, particularly Lady Caterham.
In the series, Lady Caterham’ bitterness stems from the death of her son, Tommy, in the war and the later loss of her husband. She feels betrayed by her country and sees the stolen formula as a way to secure her family’s financial future.
“She’s retreating into herself, and so it becomes a very intimate resolution to the story,” Chibnall said about the final confrontation. “It’s really just the two of them in the train carriage, and it’s about mother and daughter, but it’s also about the whole story of the decade that preceded it”.
This focus on emotional reality was key for the actors. Mia McKenna-Bruce, who plays Bundle, emphasized that the team always returned to the question of why their characters were acting. For Bundle, her investigation is powered by love for the people she has lost and a refusal to let their deaths be unexplained.
Other Key Differences in the Adaptation
Beyond the major villain twist, several other updates were made to refresh the story for modern viewers:
- The Inventor: The valuable formula in the book is created by a German inventor named Herr Eberhard. The Netflix series changes this to Dr. Cyril Matip, a Cameroonian inventor, broadening the story’s perspective.
- Bundle’s Destiny: The ending of the book sees Bundle marrying her friend Bill Eversleigh. The series omits this romantic ending. Instead, it focuses on Bundle being recruited into the secret Seven Dials Society by Superintendent Battle, taking the place once held by her late father.
- A Modern Feel: Despite the 1920s setting, the cast worked to make the characters relatable. Martin Freeman, who plays Superintendent Battle, noted that the script felt timeless. He credited this to both Christie’s original talent and Chibnall’s writing.
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A Gateway to Christie for New Fans
For Chibnall, the goal was to honor the source material while making it exciting for both longtime Christie readers and newcomers. He described the novel as a “gateway drug” into reading for him as a child and hoped the series could serve a similar purpose today.
“What we’ve talked about from the start was: ‘Can we make a treat that all Agatha Christie fans will love, that people who’ve never seen Agatha Christie will love,’” Chibnall explained. The aim was to create a “rollicking good time” that could bring Christie’s work “back into the light”.
The series is now streaming globally on Netflix, offering a new take on a classic puzzle that asks what happens when the mystery you are solving leads directly to your own front door.
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