The narrative thread of the series "One August Night" unfolds from the murder of Anna Petraki (Evgenia Dimitropoulou) by her husband Andreas Vandoulakis (Yannis 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...

As Maria's meetings with Andreas continue, a new prisoner, Markos, comes into conflict with Andreas, which seems to dangerously escalate day by day and become uncontrollable. Maria, on the other hand, is confronted with her daughter's questions regarding the past that has been hidden from her. For the first time, Maria talks to Sofia about Spinalonga. Meanwhile, in Piraeus, Manolis by chance meets a young woman from the neighborhood of Troumpa, Rinio, while he receives an unexpected visit from an unknown girl who asks for his help. An unexpected friendship begins to develop between Agathi and a former prostitute, Giota.