Hanging On

 was the twelfth and final episode of Series 4 and the 52nd episode overall.

Plot
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.