10 Kalpanakal unfolds as a narration by a former SP, Shazia Akbar Meera Jasmine, addressed to students of law and criminology. She recounts the strangest case of her career, a complex web that weaves together forest officer Davis George [Anoop Menon], Davis's family, and a girl named Angel, whom Davis treated like a daughter, with a chilling psychopath named Victor Prashant Narayanan. Angel is found dead in a forest after a festival, and though Shazia, the police officer, steps into the investigation with determination, she cannot solve it at first because there isn’t a clearly convincing motive or suspect to pin it on.
Years later, the lens shifts back to a second, more unsettling thread: a probable psychopath who abducts girls and women, locks them up in his house, and brutalizes them before ending their lives. Victor maintains a disturbing habit of storing photographs of his victims, and among his private gallery is a photo of Angel. This eerie discovery compels Shazia to reconnect with Davis, and together they push to extract the truth from Victor. Davis remains wary of Vakkachan Joju George, a man he distrusts, but Vakkachan staunchly denies involvement and even warns that Davis risks tarnishing his own reputation if he presses too hard. In a chilling twist, Victor asks for a direct conversation with Davis and confesses that he was only an eye-witness to the murder, naming John, Davis’s son, as the killer.
Heartache and doubt churn as Davis clings to the possibility that John could not have done it, yet the weight of circumstantial evidence grows heavier. John comes home late, he keeps a disturbing stash of photographs connected to Angel, and his tense demeanor whenever he returns only deepens suspicions. In a stark, morally fraught moment, Davis drags John to a statue of Jesus, urges him to beg for forgiveness, and draws his revolver, a gesture that could end his own son’s life. John, however, reveals that he did meet Angel on the night she died, though the last time he saw her was before returning home—an admission that reshapes but does not settle the case.
On the journey to the courtroom with Shazia, Victor drops a final bombshell: the confession about John was a calculated ploy to mislead Davis and cloud his mind with emotion. The court ultimately relieves Victor of all accusations due to a lack of tangible evidence, a decision that leaves Shazia feeling that a crucial thread remains unresolved. She finishes her formal address, then visits Davis, whose house sits near the institution where she lectures. The two share a poignant moment of uneasy camaraderie as she departs, but returns to find that Davis has imprisoned Victor. Victor pleads with Shazia to persuade Davis to kill him, yet the two exchange a quiet, knowing smile before she walks away, leaving Victor to endure the consequences of his acts.
