December 1942. England is in the throes of World War II. The country's motto, "Loose Lips Sink Ships," is not to be questioned. Anyone working in the Special Operations Executive office has additional reasons not to speak about their work on sabotage: it is seen as ungentlemanly and therefore not British.
Elizabeth oversees the Special Operations training program, welcoming recruits for their final honing before they parachute behind enemy lines to join the resistance or are deployed on sabotage operations. Yet loose lips, sink ships. She doesn't know the details about any of the other Special Ops missions unless she needs to know. It's best that way and keeps her heart under wraps.
Elizabeth is dancing one evening at a club with Squadron Leader Collins when her sister Jane appears. The ladies are pleased to be introduced to his colleague, Flight Lieutenant Charles Bingley. But Charles Bingley's friend isn't so pleasant, likening Elizabeth to the type of girl who poses for pin-up pictures.
When Major Darcy showed up at the Baker Street office the next day, Elizabeth is flustered to know he will be working there for the foreseeable future. The two clash constantly, even as her sister and his friend show signs of falling quickly in love. Elizabeth is thrown as to her thoughts about William when he helps gets her underage sister home from a club after Lydia snuck out.
William Darcy is a man caught between worlds. His father is English, but his mother is Greek. Since the outbreak of war, he has fought the Nazi scum in Greece on the Aegean peninsula during the final days of battle in 1940 before spending time with the Greek exiles in Egypt. Then he traveled to America to work training programs as a liaison. But now he's back in England.
Around them, the war rages while the Baker Street team carries on living like there is no tomorrow. Missions are planned. People are trained. Men and women are deployed, often never to be seen again.
But an incident from her past leads her and William on a mission together. Though her role is small compared to the dangers he faces, it's a change to her routine of tea and typing. Past hurts have made her live in the moment, self-contained and focused, an efficient secretary. But Elizabeth realizes that she needs to live like a lifetime of tomorrows awaits them despite the war.
