Every Monday evening, six people gather in a smart North London house to talk about shame. All they have in common is a history of addiction. But when one of them is murdered, it quickly becomes apparent that someone else in that circle is responsible. The investigation is hampered by the strict confidentiality that binds these individuals and their therapist together, which makes things difficult for Detective Inspector Nicola Tanner, a woman who can appreciate the desire to keep personal matters private. If she is to find the killer, she will need to use less obvious means.