Under Suspicion

Tony and Frank are assigned to monitor Powers' house in Brighton toward the end of the 1950s. Tony enters the house and resumes his affair with Hazel as Powers returns unexpectedly. In the ensuing chaos, Powers shoots and kills a police officer, Colin Grace.

Two years pass and Tony has left the force, working as an unsuccessful private detective who fakes adultery evidence for divorce cases. He extorts money by insisting on expensive hotels and substitutes his wife for a real prostitute in his schemes.

Tony collects a new customer and carries out his routine to photograph a couple in bed, only to find they have both been shot dead. The victim is Stasio, a painter seeking a divorce to marry Angeline. Stasio's will leaves everything to Angeline, not Selina.

Tony and Frank begin separate inquiries into Stasio's murder. They visit Angeline and Selina to understand relationships and motives, and to learn about the will and the divorce plans.

Tony and Angeline begin a romance while the investigation unfolds. He discovers that Stasio imprinted his thumb on his paintings to prove authenticity, linking the murder to the painter's art.

Tony uses his time in shared spaces to search Stasio's studio for evidence that could tie the murders to the paintings and to the thumb-imprinting method.

Suspicion falls on Tony when the gun used in the hotel murders is found in the hotel furnace and traced back to him. Frank and others push to clear his name while investigators close in.

Frank pressures Roscoe to reveal evidence, but Roscoe commits suicide and leaves a note implicating Tony in the murders, deepening the case against him.

Tony is arrested and tried for the murders; he is found guilty due to motive and deception. Angeline unexpectedly testifies about the rooftop escape and a distinctive lighter gesture used by the killer.

On the eve of his hanging, Frank returns to Stasio's house and finds Stasio's thumb inside Angeline's paint box. He races to the prison to stop the execution.

Angeline is arrested attempting to flee the country and is tried for Stasio’s murder, further complicating the case and the courtroom battles around the murder chain.

Tony plans to leave the country and visits Angeline in prison. She suspects that Tony and Selina conspired to frame her, creating a rift that unsettles the case.

Tony travels to Miami where he meets Selina, who has begun releasing Stasio's paintings onto the market. She hints at money and past loyalties, chastising Tony for loving Angeline and delaying the thumb planting.

In the closing moments, Tony is seen using his lighter in the manner described by Angeline in court, leaving his fate and guilt open to interpretation as the story ends.