In 1906 London, the casualty room of the London Hospital deals with a wide variety of cases. As a charity hospital, they refuse no one and are also located in the East End where the working poor are in the majority. The cases include a man whose tried to take his own life; a young boy, Teddy, with rickets; and a Russian immigrant and supposed anarchist, Abraham Goldman, who was beaten by the police.

Nurse Ada Russell has to decide whether or not to take the job of Ward Sister of Wellington ward, as it threatens to spoil her engagement to Dr James Walton. The hospital is using a radical new technique, ultra-violet light, to treat skin disease caused by unsanitary living conditions in the East End. Queen Alexandra visits with her sister the dowager empress of Russia to see the hospital.

Probationer Ethel Bennett goes through a night of rising tension as she nurses Thomas Hooley, the injured docker whose leg wounds are not healing. She clashes with ward sister Ada Russell, who is overwhelmed by the strain of running of a large, busy ward and worried about her true feelings for her fiance. Nobby Clark, leader of the violent Blind Beggar Gang, is hospitalised with alcoholic cirrhosis of the liver, aged just 15. Driven mad by cravings and nightmares, his path crosses with Ada with unexpected results.

With the hospital facing imminent financial collapse, chairman Sydney Holland launches an inspired campaign to raise money. The cost of building the modern city is revealed when workers on the new Rotherhithe Tunnel are admitted with agonising diver's bends. Ethel, working in the receiving room, contracts scarlet fever from a patient.

Revolution grips the East End as an explosion brings fears of a bomb, and Ethel Bennett and Dr Millais Culpin struggle to control the angry victims. When detectives arrive, Matron Luckes and Chairman Sydney Holland fear the hospital is in danger of becoming an extension of Scotland Yard. Meanwhile, Sister Ada Russell battles with irascible star surgeon Mr Henry Dean, whose addiction to cocaine is an open secret. And ambitious young Dr Ingrams faces catastrophe in the operating theatre.

A scandal brews as Nurse Goodley suspects that Mr Dean is ignoring the terrible side-effects of a new anaesthetic, and battles internally as whether she should risk everything and turn whistleblower. Sister Ada Russell copes with her first day in reception following reassignment. Nurse Bennett fears that her secret alliance with Dr Culpin has been discovered when Matron Luckes sends her into private nursing.