Line of Duty (season 5)

As a result of the police's mistake during a counter terrorists' operation, an innocent person was killed. Detective Inspector Steve Arnott refuses to take part in the concealing of the crime. After that, he was transferred to the anti-corruption unit that was headed by Ted Hastings. The superior tasked Arnott to investigate the case of a senior officer of the central police unit. He had recently become the officer of the year.