December 1943, following the death of a Polish SOE agent in suspicious circumstances at a training school in Arisaig, Kalisz is flown out of Poland and brought to Britain, where Winston Churchill himself assigns Kalisz the task of solving the case.

Krystina Kowolsk, the agent, was a key intelligence officer and an aristocrat firmly established in Polish society. She had been a bridesmaid at Zofia Sikorska’s wedding, whose father, General Władysław Sikorski, was the prime minister of the Polish government-in-exile. Both were killed in a mysterious plane crash nine months earlier.

It is therefore a delicate time for the British alliance with Poland, as the Poles already fear they will be abandoned to Russia. With the death of the Polish Prime Minister, Churchill is determined to prevent yet another mysterious death from muddying the waters and undermining the trust and faith that hold the alliance together.

Winston Churchill therefore needs Kalisz, a Pole, to carry out the investigation so there can be no inference of a cover-up. The stakes could not be higher, as Kalisz is sent to the most dangerous place in Britain, where training accidents are commonplace and everyone is taught both to kill and to resist interrogation.

Kalisz quickly establishes that Krystina Kowolsk was murdered, but a second death is also connected to the case when the body of Jean-Marc, a French Canadian, is discovered with a bullet wound to the head. Jean-Marc was infatuated with Krystina, and the top brass attempt to push for an open-and-shut case of murder-suicide.

Undaunted, Kalisz begins his inquiries into the staff and students of the training centre. Douglas Jackson takes the reader through a hall of mirrors, where secrets are hidden within secrets, and the suspects have assumed identities and something to hide. Questions begin to be asked about Krystina Kowolsk’s loyalty and mental state, after she had suffered appalling tortures at the hands of the Gestapo on a previous mission. As Kalisz resolves one strand of the investigation, another reveals itself as he delves deeper into the wartime black ops of the SOE, increasing the danger he is in.

While Kalisz is busy trying to keep the Anglo-Polish alliance together, back in Poland his family are left holding the fort against threats closer to home and gain a greater insight into Kalisz’s world of shadows.

Blood Vengeance is an absorbing novel that examines the dark recesses of the war and the men and women who had to take unimaginable risks, as we are taken through the labyrinth of Kalisz’s investigation. In Kalisz, Jackson has created a classic, methodical detective who keeps his humanity and integrity while being caught between the two worlds of his German and Polish parentage.