A West Virginian mother, burdened with anxiety, waits daily for updates regarding her two sons fighting overseas. At the same time, childhood friends Lena and Abram, portrayed by Ebony Obsidian and Gregg Sulkin, navigate the challenges of their blossoming romance in 1940s Philadelphia, grappling with societal prejudices as Lena is black and Abram is Jewish. Their love story takes a tragic turn when Abram is commissioned as an officer pilot and tragically dies shortly thereafter, leaving the heartbroken Lena with no choice but to enlist in the military following her graduation.

On her journey to basic training in Georgia, Lena meets a group of fellow enlistees who will soon become her lifelong friends. They are guided through their grueling training by Captain Charity Adams and Lieutenant Noel Campbell, played by Kerry Washington and an undisclosed actor respectively. Despite their rigorous preparations, the battalion finds itself waiting in vain for orders.

In the heart of the White House, a persistent West Virginian mother takes the courageous step of confronting Eleanor Roosevelt, performed by Susan Sarandon, about a pressing issue—no one across the country is receiving mail from the frontlines of war. In a critical meeting that includes President Roosevelt, played by Sam Waterston, and Mary McLeod Bethune as brought to life by Oprah Winfrey, it is revealed that the rampant issue of undelivered mail stems from a logistical debacle requiring prioritization of supply transport over personal correspondence. As essential letters and packages languish in hangars across Britain, Bethune insists that the Black Women’s Army Corps, including Captain Adams’ unit, is capable of undertaking the monumental task of resolving the backlog.

Soon enough, the battalion boards the ocean liner Île de France, crossing a treacherous Atlantic without naval protection. Upon arriving in Glasgow, they confront an unsympathetic commanding officer, General Halt, portrayed by Dean Norris, who subjects them to a strenuous march through the city. They are taken to a decrepit boarding school that will serve as their makeshift base, grimy and plagued with rats, far from the warm comforts of home.

Under the leadership of newly-promoted Major Adams and her trusted second-in-command Captain Campbell, the soldiers face an impossible six-month deadline to transform the dismal boarding school into a functioning post office and barracks, tasked with the monumental job of sorting through a two-year backlog of mail. As they toil to create a semblance of livability, Lena experiences a moment of emotional turmoil upon witnessing careless handling of personal dog tags in damaged letters, leading her to confide in her friends about her profound connection to Abram, emphasizing the importance of their mission. Adams, realizing the significance of Lena’s story, becomes even more driven in her leadership.

As the battalion sorts through the mountains of undeliverable mail, they are given an unexpected assignment to host African-American soldiers to help bolster morale. Lena encounters Hugh, a fellow soldier she previously met, and they share a dance, though she finds herself retreating when a poignant song reminds her of Abram. They mutually agree to remain friends, navigating their feelings amidst the ongoing war.

The situation worsens when the vigilant battalion discovers letters that have been opened, showcasing the various challenges they face—the maze of identical names, shifting soldier units, and mold-damaged letters present insurmountable difficulties. Tragedy strikes again as they mourn the loss of two comrades in a bombing incident on their way to the school, culminating in Lena receiving a long-awaited letter from Abram after his burial, finally granting her the closure she desperately sought.

Confronted by General Halt, who questions Major Adams’ competency, she bravely stands her ground, declaring “over my dead body” when he suggests replacement with a white male officer. Motivated by her courage, the soldiers rally behind Adams, clapping fervently in support of their indomitable leader.

As General Halt attempts to push for Major Adams’ court martial, he’s interrupted by cheers from the battalion, who triumphantly announce the arrival of their sorted mail—over 17 million pieces have been organized in a mere 90 days despite the myriad obstacles. Following this remarkable achievement, the 6888th is sent to Rouen, France, to tackle another mounting mail crisis. In the end, Lena finds happiness as she marries Hugh, ensuring their love continues beyond the war.

Despite their extraordinary accomplishments, the women of the 6888th faced a lack of recognition upon their return to the United States. It was only years later, during a ceremony led by Michelle Obama, that their contributions were duly acknowledged. The legacy of the 6888th lives on, with US Army Base Fort Lee partially renamed in honor of Major Charity Adams.