What Really Happened to Steve Nathan

While going through her elderly mother's things, Lindsey Casselton discovers a photo of her mother in the arms of a stranger. The photo is dated nine months before Lindsey was born. The father she grew up with is dead and her mother has Alzheimer's, which leaves Lindsey no option but to embark on a life-changing journey to learn about her birth father-a CIA operative in Vietnam, who went missing at the end of the war.
On the other side of the country, Nate Huong has a challenging youth and eventually finds his way as a restaurant owner with his Vietnamese mother Mai as head chef. When he goes to his mother's homeland, Nate learns disturbing new details about his American father-a CIA operative, who was last seen at Mai's family's homestead.
The two half siblings, Lindsey and Nate, meet in Vietnam by chance during Tet at a coffee plantation in the highlands. After combining their knowledge and uncovering more at an explosive gathering with Nate's Vietnamese family, they learn what really happened to their father, Steve Nathan, after he left Saigon and drove into the encroaching North Vietnamese army, never to return.