The narrative thread of the series "One August Night" unfolds from the murder of Anna Petraki (Evgenia Dimitropoulou) by her husband Andreas Vandoulakis (Yiannis Stankoglou), one night in August, six years ago, when the latter learns that she had a lover, his cousin Manolis Vandoulakis (Yorgos Karamihos).
The main role in the series is played by Anna's sister, Maria Petraki (Youlika Skafida), who tries to continue her life, keeping well-hidden secrets that must not come to the surface...

Maria, secretly from her husband, Nikos Kiritsis, visits Andreas, her sister's killer, in prison. This arouses the curiosity of the chief constable, officer Ntretakis, who begins to show a strange interest in her. Andreas and Maria meet for the first time in years, and Andreas' gratitude for the woman who visited him is immense. He begs her to come again. Meanwhile, Manolis' dangerous course, which is getting closer and closer to self-destruction every day, makes his landlady Agathi make a decision to try and save him.