DI Lou Slack attempts to make amends for her misdeeds but to do so she must betray the dangerous drug baron she has been working for.

When Lou fails to warn Col about a police raid, he decides to test her loyalty.

Lou and Vernon's plans to take Col down threaten to trigger a bloody gang war, while Owen and Donal grow ever closer. Esther becomes curious about Lou's erratic behavior.

Lou makes one last desperate attempt to bring Col down, but things do not go exactly as she hoped. Feeling powerless, Ceri resorts to drastic action in order to defend his family.

As Vernon is taken into custody, Lou attempts to live a normal life within the law and deal with suspicion from Sandy but finds herself pushed to breaking point.