A clandestine affair between two lovers spirals into a harrowing legal investigation following the discovery of a series of suspicious deaths. Tony Falcone, a man trapped in a suffocating marriage and a small-town existence, engages in a passionate, illicit relationship with Andrée Desormes. Their secret meetings in the titular blue room become the catalyst for a sequence of events that leaves multiple people dead. The narrative framework utilizes a non-linear structure, oscillating between the intense, claustrophobic atmosphere of the affair and the clinical, detached environment of a courtroom interrogation. Tony must navigate the mounting evidence against him while grappling with the psychological manipulation exerted by his lover and the judgmental gaze of his provincial community.

Readers frequently highlight the stark, economical prose that defines this work, noting how it heightens the sense of unease throughout the narrative. Discussion often centers on the moral complexity of the characters and the way the author avoids clear-cut definitions of guilt or innocence. Critics often point to the effective use of the courtroom setting to expose the hypocrisy of the surrounding community. Many readers find the pacing to be deliberate and methodical, which serves to emphasize the protagonist's growing isolation as the legal net tightens around him.