After a fatal stabbing in a crowded market place, the pressure is on to make Londoners feel safe again. Ronnie and Joe have a new boss to contend with, DI Elisabeth Flynn is determined to put her stamp on the MIU, declaring her own personal crackdown on knife crime. Under pressure from all sides, Ronnie and Joe struggle to gather enough evidence to charge the youth they believe to be responsible. However, when the suspect inadvertently confesses to Ronnie, he thinks he's got him – but with the confession uncorroborated by anyone else, Ronnie begins to realise that his honesty is in question.