"Hanging On" is the 52nd episode of Casualty and the 12th and final episode of the 4th series. It was preceded by "Banking for Beginners" and followed by "Penalty". The episode was directed by Steve Goldie and written by Sam Snape.
Alex is given a surprise leaving party at the end of shift and given champagne from a bed pan. But a bomb explosion in the city centre puts the team on red alert. Two surgeons, Arnold Richardson and Simon Spencer, arrive to assist the team, who help treat a stream of injured patients. Two schoolgirls, Janet and Anna, are brought in after a school trip to a panto. Janet has minor head injuries, but Anna is taken to the operation theatre for a laporotomy. Her mother, Gill, waits agonisingly until they finally tell her she's alright. Their teacher's husband, Mr Marshall, is frantically searching for his wife. Cyril discovers one patient is a shoplifter as her bag is full of jewellery. Jimmy waits with the bodies. Under a sheet, a mobile phone rings. He tells the worried wife he'll get her husband to call back.