In May 1966, 20-year-old Frances “Frankie” McGrath attends a going-away party for her older brother, Finley, at her parents’ house on Coronado Island in California. Born into wealth and raised to valorize military service, Finley has volunteered to serve in the ongoing Vietnam War. Frankie feels conflicted about her brother’s departure. During the party, she slips into her father’s office and views his heroes’ wall, which contains pictures of male family members who served their country. Finding Frankie there, Rye Walsh—one of Finley’s naval academy friends—tells her that “Women can be heroes” in the modern world. In subsequent months, Frankie writes to Finley and graduates early from her nursing program. At her hospital job, she meets a Vietnam veteran who credits a woman nurse serving abroad for his survival. Inspired, Frankie volunteers for the Army Nurse Corps. Frankie’s impulsive decision distresses her parents, who believe war is only for men. During their argument, naval officers arrive with news that Finley has been shot down in a helicopter. Mom urges Frankie to stay home, but she can see no way out of her commitment.
Frankie flies to Vietnam in March 1967. Frankie’s arrival is disorienting and the 36th Evac Hospital is not the orderly facility she anticipated. Frankie has two bunkmates, an emergency room nurse named Ethel Flint, and a Black surgical nurse named Barb Johnson. At the hospital’s officers’ club, Frankie meets Jamie Callahan, a handsome surgeon who comforts her during a sudden series of explosions. The next day, Frankie gets thrown into the emergency room to help with a mass casualty (MASCAL). Helicopters deliver wounded soldiers with horrific injuries. Frankie feels useless, but Ethel encourages her to do what she can and learn. Frankie is officially assigned to the Neuro ward, where she hones her skills under the tutelage of Captain Ted Smith. One day, she and other medical staff visit a Vietnamese village to care for locals, an initiative called Medical Civil Action Program (MEDCAP).

Jamie convinces Frankie to transfer to surgery, where he mentors her. Frankie considers a romance with Jamie until she learns he is married. Mom writes to Frankie about the increase in anti-war protests. On a visit to an orphanage, Frankie cares for a South Vietnamese girl whose village was bombed by their supposed American allies. Jamie’s helicopter is shot down and Frankie assumes he is dead. Mourning Jamie and Ethel, who has gone home, Frankie and Barb transfer to the 71st Evac Hospital, which sees heavy combat casualties. Despite significant casualties, America keeps sending troops and proclaiming certain victory.
In January, the Viet Cong launch a coordinated attack on several military bases, and the desperate need for nurses inspires Frankie to sign up for a second year. While on leave, Frankie has sex with Rye, who has broken off his engagement. For the next year, she copes with increased wartime violence and fear for Rye, who is a helicopter pilot. In March 1969, Frankie flies back to the United States, hoping Rye will follow her soon after.
Frankie’s return to America is unpleasant. Protesters shout at her in the airport and she has intense nightmares about Vietnam. Frankie’s parents don’t want to hear about her wartime experiences, and Dad has lied to their friends, saying Frankie has been in Florence. No one believes she served in Vietnam. Frankie visits Rye’s father to plan a homecoming party, only to learn Rye has been killed in action. Frankie sinks into a depression until Ethel and Barb visit and remind her how much she loves nursing. She takes a hospital job but becomes frustrated with management’s lack of trust in her skills. Mom forces Frankie to socialize with her old society friends, but Frankie finds she can no longer connect with those women. That same day, Frankie is fired for performing an emergency tracheotomy when there were no doctors available. The next day, Dad scolds Frankie for exposing his lie about Florence. Furious at Dad’s refusal to acknowledge her heroism as a woman, Frankie destroys his heroes’ wall and blames him for Finley’s death. Dad kicks Frankie out. She seeks help at the Veterans Administration Clinic, but the psychiatrist insists there are no women in Vietnam and tells her to forget the war.
For the next two years, Frankie lives with Barb and Ethel on a farm in Virginia. By April 1971, she has found another nursing job, and her nightmares are less frequent. News of the violent My Lai massacre has deepened the public’s anti-war sentiment. Nevertheless, President Nixon continues to send troops to their deaths. Barb has joined the Vietnam Veterans Against War (VVAW) and cajoles Frankie into attending a protest in Washington D.C. During the march, Frankie is furious to learn that even veterans dismiss her service. The demonstration awakens her own anger at the government. At another protest, veterans throw their war medals on the Capitol steps. Afterward, Frankie meets Henry Acevedo, a California psychiatrist who opposes the war and asks if she has nightmares. Frankie and Barb attend a fundraiser for the League of Families, run by Navy wives whose husbands are prisoners of war. One woman recognizes Frankie from Coronado and expresses sympathy about Mom’s recent stroke, which nobody had told Frankie about.
Frankie returns to California to care for Mom. Dad confesses his difficulty accepting who Frankie became in Vietnam. He and Mom gift Frankie a cottage nearby. Frankie volunteers with the League of Families, writing letters and selling POW bracelets. On July 4, Mom and Dad host a lavish party which Henry Acevedo happens to attend. A firecracker triggers Frankie’s flashbacks to Vietnam. Henry takes her home and they start a relationship. In December, Frankie realizes she is pregnant and agrees to marry Henry despite still being in love with Rye.
In January 1973, Nixon signs the Peace Accord, ending the war. When the first POWs arrive home from Vietnam, shockingly, Rye is among them. Frankie is devastated to learn he lied to her and is married. In her distress, Frankie miscarries the baby and calls off her engagement with Henry. To cope, she turns to alcohol and pills and withdraws from family and friends. The hospital puts her on leave for erratic behavior. Eventually, Frankie reconnects with Rye, and they begin an illicit affair. Though Rye proposes to Frankie, she discovers he’s fathered another child with his wife. Spiraling, Frankie drives after taking Valium and nearly kills a cyclist. Ashamed, Frankie unintentionally overdoses and nearly drowns in the ocean. Dad places her in a psychiatric ward. From there, Frankie is transferred to Henry’s clinic, where she learns many veterans are prone to addiction as a result of post-traumatic stress disorder. She begins therapy with Dr. Alden and progressively unpacks her trauma. Frankie leaves the facility in 1974 and settles in Montana shortly thereafter.
In 1982, Frankie has transformed her Montana ranch into a haven for women veterans from Vietnam. She attends the dedication for the Vietnam Veterans Memorial in Washington D.C., where she, Barb, Ethel, and so many others finally have their sacrifices recognized. Her parents come to see Finley’s name, and Dad apologizes to Frankie, who he now understands is a hero. Observing the monument, Frankie runs into Jamie Callahan, who survived his injuries. Frankie feels proud of her service and validated to be among other veterans.