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The film starts with an animated sequence, showing an anthropomorphic turtle walking down a road, while picking up a flower and smelling it. A chorus sings the Duck and Cover theme:
Leeds' character is "Anne Lester", a young orphan who is trying to pay for her brother's college education. After meeting Markey, a drug dealer, Anne begins to believe that she must smoke marijuana to fit in with her friends. She then goes to a "tea party", where she tries the drug for the first time. She is unaffected by the initial experiment, and loses her fear of drugs as she continues to smoke.
The cartoon states that, annually, 118,481 babies out of 2 million will die before reaching their first birthday. Thus, the cartoon shows John E. Jones, a baby that may add to this statistic if not given proper healthcare. The cartoon proceeds to show most of John's life, including his school years, marriage, later life (as a father), and his golden years, providing other helpful health information along the way. Before the cartoon ends, however, it returns to John as a baby, reminding the audience that John needs proper healthcare to survive. The cartoon then states that if every American paid just three cents a week, sufficient healthcare could be provided for John and babies everywhere.
Bouleversant témoignage sur les horreurs de la guerre censuré jusqu’en 1980, Que la lumière soit est aujourd’hui considéré comme l’un des meilleurs films jamais réalisés sur les conséquences psychologiques de la guerre.
The film uses animated diagrams to detail the menstrual cycle. The film's narrator, who is not identified in the credits, informs the viewer that "there is nothing strange or mysterious about menstruation", and it shows women engaged in such activities as bathing, riding a horse, and dancing during their menstrual cycles. The film's narration by actress Gloria Blondell also provides advice to avoid constipation and depression, and to always keep up a fine outward appearance.