A seriously ill patient is brought to the clinic of a research institute. Young doctor Falko, a resident at the institute, insists on an urgent operation, but his supervisor Druz believes that in this case therapeutic treatment will be more effective and, moreover, will not be associated with risk. Professor Shostenko nevertheless undertakes to operate on the patient. The successfully completed operation confirms the diagnosis made by Falko. Parallel to the events in the clinic, the action unfolds in the house of the director of the institute Shostenko, where his son Igor returns after a three-year absence. The complicated relationship between Igor and his wife, the love story of Shostenko's daughter and Druz - the canvas of the second plot of the film.

Based on the novel of the same name by Yurii Mushketyk. For the second year, a laboratory headed by professor Marchenko has been working on the problem of photosynthesis. The work absorbs the entire team – each new result seems to confirm the correctness of the leader’s theory. The scientist Borozna, convinced that his colleague’s research path is mistaken, makes it clear to a doctor that it is time to stop and take a more critical look at the results.