Two unlikely partners must risk their secrets—and hearts—to unravel a web of treachery and save England.

Miss Simone Delacourt, a seemingly unnoticed wallflower in the eyes of the ton, hides a secret life as a spy, enjoying the freedom her anonymity affords. When she's reluctantly paired with Mr. Caleb Bolingbroke, a man she can barely tolerate, her carefully crafted life is thrown into turmoil.

Mr. Caleb Bolingbroke isn't pleased that he is assigned with the obstinate Miss Delacourt, but he is pleased when he is able to convince her to give their partnership a chance. Pursuing elusive French spies is their shared mission, and the stakes are high. Despite Miss Delacourt's initial mistrust, Caleb is determined to win her over.

As they delve into the pursuit of the French spies, Caleb and Simone discover the need to depend on each other. The case unravels a web of secrets and lies, challenging their perceptions. In this intricate game of treachery, they must risk everything, including their hearts, to save England from an impending threat.