The health department protects the community by isolating the case. The health department nurse advises about isolation. After treatment, Mary is well again and is seen playing with her friends. Statistics are given about the efficacy of the antitoxin when given at different stages in the disease. Children are seen being immunised at one year old. Children who were not immunised at this age are shown being immunised at school. Six months after immunisation the Schick test is administered to check whether the children are now immune. The Schick test is read. The film ends with the intertitles stating that some cities have not had a diphtheria death in five years.