Silent Witness S01E05 - Darkness Visible, Part One

A man is found dead in his cell. It is clear that he has been murdered. Sam comes to the conclusion that one of the officers who was in the police station at the time of death has to be the killer. A police officer is also found dead, the conclusion is that he killed the man and then committed suicide. Sam thinks that they are both murders and tries to solve the case by finding the real perpetrator of the murders.