Cnut - Busman's Holiday

Cnut is blithely unaware that the calm he and Ilse are experiencing foretells a massive storm, where bombs and bullets become the norm. She learns that her aunt is dying in Padua, and flies to Italy, to be with her at the end. Cnut goes on what he expects to be a  peaceful, extended fishing holiday, with his old friend and predecessor in his job, Jens Jensen, in the small coastal village where he lives.
Jens tells him that a construction company wants to build a marina where the cottages are, and has offered three times their value to anyone wanting to sell. Some do, but those that do not begin to receive escalating threats. Then a prostitute is murdered, but her death does not appear to be connected with the threats. Her murder was observed by a lad with a mental disability, and his throat is cut to prevent him talking.
Further murders follow, with fire bombings and explosions - one intended for Cnut and Jens they avoid by sheer chance, but others are not so lucky. Cnut's sixth sense is initially the only reason for his suspicion that he knows who is behind the deaths, but then one tiny clue hardens that suspicion enough that he takes a far more drastic step for confirmation. The certainty has him facing a dilemma no cop wants to face.
He knows that if he does not take action that could put him behind bars for the rest of his life, more murders will occur. It does not stop him from taking that action.