Is Dept. Q based on a book? Explained

Dept. Q is a Scottish crime thriller series that was released on May 29, 2025, on Netflix. It is not based on a true story but is adapted from the first book of the Danish author Jussi Adler-Olsen's book series, which was released between 2007 and 2023.

Created by Scott Frank and Chandni Lakhani, the series features nine episodes, which are directed by Scott Frank and Elisa Amoruso. Lakhani, Frank, Stephen Greenhorn, and Colette Kane serve as its writers. David Brown has produced the series, while Frank, Andy Harries, and Rob Bullock serve as its executive producers.

The official synopsis of the Dept. Q, as per Netflix, reads,

"A brash but brilliant detective (Matthew Goode) leads an Edinburgh cold case unit in this tartan noir by the writer and director of "The Queen's Gambit."

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Dept. Q is not based on a true story

The plot of Dept. Q is adapted from the Danish author Jussi Adler-Olsen's 2007 novel Mercy (UK) or The Keeper of Lost Causes (US). The story is a work of fiction and is not inspired by true events.

The Netflix series stays largely true to the source material and, most notably, deviates only in its setting. The book is set in Copenhagen, Denmark, while the series takes place in Edinburgh, Scotland. Another change involves Merritt Lingard, whose abduction and search form the crux of the story. She is written as a politician in the book ,but is depicted as a prosecutor in the series.

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What is the story of Dept. Q?

Detective Carl Morck is tasked with establishing the cold-case unit, Department Q, in Edinburgh following a traumatic past incident which led to the death of his fellow police officer. The Syrian cop Akram Salim, and the young cadet Rose Dickson become his allies in his search for missing individuals who have been long forgotten.

For their first case, they investigate the disappearance of Merritt Lingard, a high-profile prosecutor who was kidnapped from a ferry cruise four years ago. While digging into her past, the team learns about her relationship with the journalist, Sam Haig. Further investigation reveals that Merritt's boyfriend was an impostor named Lyle Jennings, as the real Haig had died in a climbing accident months prior.

Sam and Lyle had first met at an institution for troubled boys. When they ran into each other again years later, Lyle killed Sam and stole his identity. He pursued Merritt as Haig, intending to date her and eventually kidnap her to avenge his brother Harry's death.

The series reveals that Merritt had dated Harry as a teenager and had planned to run away with him to escape their troubled family lives at home. Merritt helped Harry and Lyle steal her mother's jewelry so that the couple could make a fresh start elsewhere. When Merritt's brother, William, caught them red-handed, Lyle beat him to a pulp and left him disabled for life. But Harry was chased down by the police and was killed while escaping.

In the climax of Dept. Q, the team finds Merritt at the Jennings’ shipping company, Shorebird Ocean Systems. They're shocked to discover she’s been trapped and tortured in a hyperbaric chamber for four years. They carefully release the pressure and rescue her before she can reunite with William.

In the end, Lyle is dispatched by Akram, and his mother, who was his accomplice in the kidnapping, shoots herself to escape getting captured.

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Viewers can stream all episodes of Dept. Q on Netflix.