The detectives investigate a string of murders. Could the killer be a police officer? Meanwhile, Rob is forced to hand over vital evidence when his family is threatened.

As the detectives investigate who murdered a schoolboy, Vivienne is forced to reveal her intimate connection to a suspect.

When a locksmith is murdered, Billie learns he was a witness to her father's death 10 years earlier. Vivienne pleads with her ex-husband to do the right thing, but he is afraid they're both in danger.

A body found in a suitcase is identified as a man who has been missing for several weeks. His widow and his brother point the finger at each other. Meanwhile, David tries to convince Mulgrew to reveal what he knows.

David and Vivienne cross a huge line, both professionally and personally.