Banks and the team begin the painful job of finding out exactly who was responsible for the incident that has affected all their lives.Following dogged police work, they locate and close in on a suspect, only to be thwarted when it's proven there's no way they are to blame. While Chief Superintendent Anderson puts pressure on Helen to reign in Banks and close the case, Banks becomes increasingly certain that this is all down to one man – crime boss Steve Richards. Banks' obsession with nailing Richards sends him over the edge, resulting in Anderson exiling him from the station and making Helen acting DCI in his stead.