Under the paper moon / Shaina Steinberg.

Enhanced descriptions from Syndetics:

Kate Quinn's The Rose Code meets Mr. and Mrs. Smith in this intrigue-filled debut, as two former spies who shared more than just missions during WWII reunite in 1948 Los Angeles. Can they let go of heartbreak long enough to team up for one last operation in this tightly-plotted, emotionally rich postwar mystery?

It's 1942, and as far as her father knows, Evelyn Bishop, heiress to an aeronautics fortune, is working as a translator in London. In truth, Evelyn-daring, beautiful, and as adept with a rifle as she is in five languages-has joined the Office of Strategic Services as a spy. Her goal is personal- to find her brother, who is being held as a POW in a Nazi labor camp. Through one high-risk mission after another she is paired with the reckless and rebellious Nick Gallagher, growing ever close to him until the war's end brings with it an act of deep betrayal.

Six years later, Evelyn is back home in Los Angeles, working as a private investigator. The war was supposed to change everything, yet Evelyn, contemplating marriage to her childhood sweetheart, feels stifled by convention. Then the suspected cheating husband she's tailing is murdered, and suddenly Evelyn is back in Nick's orbit again.

Teaming up for a final mission, Evelyn and Nick begin to uncover the true nature of her case- and realize that the war has followed them home. For beyond the public horrors waged by nations there are countless secret, desperate acts that still reverberate on both continents, and threaten everything Evelyn holds dear...