Enrico Rosseni, a married Italian teacher at a Catholic girls' school in London, is having an affair with one of his students, Elizabeth. One day while they are rowing on the Thames, Elizabeth thinks she sees a girl being murdered on the shore. Enrico dismisses her claims, thinking it's a product of her imagination. However, when one of his other students is found dead shortly thereafter, Enrico starts to suspect that Elizabeth might have indeed witnessed the crime. The murder investigation gains momentum, and Enrico finds himself at the center of suspicion. His attempts to clear his name lead him deeper into a tangled web of secrets and lies involving both his students and colleagues.

As the investigation progresses, more girls from the school become victims of the ruthless killer. Enrico’s obsession with proving his innocence intensifies, resulting in clashes with his increasingly suspicious wife Herta, and the police who are eager to solve the case. As the body count rises, disturbing details about the motives behind the killings begin to surface, suggesting connections to hidden past events and buried secrets within the school community. Faced with mounting pressure and paranoia, Enrico must unravel the mystery before anyone else falls victim or he himself is irreparably implicated.