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The Oath


A suspenseful series in which individuals are forced to choose between their morals and their duties by an acclaimed, new voice in Nordic crime fiction.

The Oath, the first book in the River Delta series, asks what happens when friendship comes up against the law?

In late autumn, a man is found dead at a summer cottage. A group of old friends have congregated for a few days of drinking, but everything goes wrong when one of the men winds up getting stabbed. When barely any mourners show up to pay their respects, it transpires that the victim has an exceptionally violent criminal background of his own. Police Commissioner Jari Paloviita, who is assigned the case, is horrified to learn that the suspect is his childhood best friend, an old classmate of Jari’s who grew up on the wrong side of the tracks, but stood up for Jari as he was relentlessly bullied at school, with the two boys taking a blood oath together.

In skilfully constructed flashbacks, Tuominen explores just how lasting the effects of our childhood traumas can be, and how the lives of two old friends can ultimately take two wildly different paths. In the end it is up to Jari to decide whether his loyalty to his friend holds more weight than his legal duty.

Henning Mankell meets Stephen King’s The Body in this touching and compelling crime novel about secrets, guilt and duty.

Arttu Tuominen (b. 1981) is a Finnish environmental inspector moonlighting as a crime writer. Tuominen was awarded the ‘Johtolanka’ Prize for The Oath, garnering praise for the novel’s cleverly constructed flashbacks and realistic dialogue, making him eligible for the Glass Key Prize. Tuominen’s writing is distinctive for giving a compassionate and relatable voice to those on both sides of the law. He lives in the south-western Finnish town of Pori with his family.


The Oath, 2019
Jeopordy, due May 2020
The Weight of the Past, due late 2021


Finnish PDF
English sample translation 75pp
Series presentation
Author letter

Prizes and nominations

2020, The ‘Johtolanka’ Prize from the Finnish Whodunnit Society


“In terms of narration, style, building suspense and depth, The Oath is the best of Tuominen’s novels so far.” – Satakunnan kansa newspaper

“Tuominen’s writing is reminiscent of Stephen King and the late Matti Yrjänä Joensuu, the great Finnish crime fiction writer. In Tuominen’s book, both the police and the other characters are multidimensional people; crimes are not committed within a vacuum and there is no external evil that is easy to blame and punish.” – APU magazine

“The Oath is a cleverly built, beautifully written tragedy and an intense thriller.”  Kansan Uutiset newspaper

“A crime novel about a school bully’s problematic family and friendship, The Oath surprised me and captured my attention immediately. The writer’s societal prowess brings depth and ethical reflection to the plot. The multi-dimensional characters are reminiscent of Matti Yrjänä Joensuu’s wonderful Harjunpää books. But this new crime series has its own strong voice. The Oath is touching and timely.” – Opettaja-lehti magazine

“The novel’s protagonist, Commissioner Jari Paloviita, is reminiscent of lots of Patricia Highsmith’s characters: one or two innocuous acts inevitably trigger a slippery slope and, once you’ve started slipping, you can no longer stop.” – The Finnish Whodunnit Society’s ‘Johtolanka’ Prize jury

“Arttu Tuominen’s new detective story is his best yet. I’d even recommend it to those who aren’t diehard crime fiction fans… It’s an unusual thriller. The novel’s crime is ostensibly about a day-to-day drunk tank. But its most thrilling parts stem from past events and a Police Commissioner’s internal moral struggle.” – Sini Kuvaja, Satakunnan Kansa newspaper