1947. Adventurous Radcliffe graduate Catherine 'Cat' Killeen cancels her wedding and upends a future that no longer suits her. At the behest of her professor and hungry for a challenge, Cat arrives in Virginia to work on a confidential military project. A student in cryptanalysis, Cat will assist in rooting out Soviet spies who have infiltrated the US. Joining the 'government girls' of Arlington Hall, Cat gains the respect of her superiors and the friendship of her peers. Then, on a night out in DC, she runs into Jonathan Dardis, her arrogant Harvard rival and newly minted agent for the FBI. What Cat and Jonathan share is a competitive drive and an attraction that's becoming just as spirited. They're also united in pursuing the same critical goal for America. Together, they're diving deep into the shadows of espionage as the stakes of the codebreaking operation grow ever higher.