Set in 1860s London, the novel follows Emily "Fido" Faithfull, a trailblazing woman running a printing press, who reunites with her old friend Helen Codrington. Helen is trapped in a loveless marriage and starts an affair with a young officer, Colonel Anderson. When the affair becomes public, a scandal erupts involving accusations of adultery and cruelty, centered around a mysterious sealed letter. The story explores friendship, betrayal, and Victorian society’s harsh judgments, leading to a tense courtroom drama that tests loyalty and reveals dark secrets.