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 Alzheimers, 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.