In Tunbridge Wells A&E an ambulance crew bring in a patient who is behaving aggressively, sister Geraldine calls security, but the patient takes off, refusing treatment. At North Middlesex University Hospital, a patient's heart stops beating, so the team tries to save their life and maintain blood flow to the brain. At the North London Emergency Department, a 45-year-old suffers life-threatening anaphylaxis from an allergic reaction.