Inspector Dumont and his deputy Inspector Queneau investigate the murder of a young woman. They learn that the victim was pregnant before her death and that she was the mistress of Mario, a shady playboy who had dumped her while she was with child. A doctor is first suspected but is he the real culprit?

This film was produced as an extension of a research film on the metamorphosis of the fly. It successively shows the hatching of the eggs, the nutrition and growth of the larvae, swarming and underground penetration, the formation of the pupa, metamorphosis and organization of the adult insect.

Doctor Pierre Thévenard presents an educational documentary on cancer, proposing diagrams on the formation of tumors, studying its development in the animal and plant kingdoms.

An interview with pioneering photographer Lucien Bull.