She decodes secrets for a living. He was sent to destroy her. Neither knows her husband is still alive. Portsmouth, 1770. Eleanor "Nora" Thorne appears to be nothing more than a quiet apothecary-measuring tinctures by day, mourning her naval cartographer husband by night. But in secret, she intercepts coded messages hidden in ship manifests, desperate to prove Thomas didn't die at sea... he was silenced. Captain Gabriel Vale once recommended Thomas for the mission that killed him. Now disgraced and hired by the Admiralty to hunt down the "Portsmouth Cipher," he never expects the mastermind to be the sharp-eyed widow watching him from behind her counter. Forced into a dangerous alliance, Nora and Gabriel race to stop a French invasion-only to uncover a conspiracy that reaches the highest levels of the British Navy. But trust is the rarest cipher of all... especially when Nora receives a message in her husband's hand: *"I'm alive. But don't trust Vale." From Seraphina Sinclair, author of The Spinster's Key, comes a slow-burn historical romance rich in espionage, emotional intimacy, and intellectual equality-perfect for fans of The Alice Network, Bridgerton's intrigue, and Mr. Malcolm's List.