The work of the Army Blood Transfusion Service is described. A male voiceover describes how they collect blood, also from residents of towns and villages. The special equipment for blood transfusions in the field is also shown. The use of blood derivatives such as plasma and serum is described. The laboratory work done to produce these blood derivatives is shown. A blood donation session in Britain is seen and the narrator explains that the blood supply depends on these donors. The use of blood in the battles of Flanders and Dunkirk as well as the Blitz is described. Transfusions are shown being given to wounded soldiers in the field. The narrator explains that now, the blood service is a national service involving many people, from doctors to donors. He also stresses that this service must not end when the war ends.