A short summary of The Affair, taken from WellRead.
A journey into his past is the backdrop for adventure sixteen of the Jack Reacher series. Set just months before his retirement as an elite military policeman, Reacher is sent to Mississippi to investigate the brutal murder of a young woman, found raped with her throat cut. Tasked with working undercover and as discreetly as possible, Reacher infiltrates the local army rangers base and finds commander Reed Riley, son of Senator Carlton Riley, a military purse holder, concealing information. Never good at following orders and advice to stay away, Reacher takes a risk and decides to work alongside ex-marine police and local sheriff Elizabeth Deveraux. Together they find this recent murder is not an isolated incident. It is the work of a serial killer, having identified two murder cold cases of two black women, never properly investigated. With the army running its own investigation, the relationship with Deveraux raising more questions as the suspected murder weapon of the one of the victims is found in her own back yard, Reacher finds his and the army investigation come to a head, with two very different answers. Returning to report to his Colonel at the Pentagon, Reacher finds his discoveries are unwelcome and fighting for his life, he kills his commanding officer. With the truth uncovered, Reacher returns to Mississippi and confronts the perpetrators. Carlton Riley is aware of his son’s penchant for murder and has been conspiring to cover for his son, using all of the power at his disposal. In true Reacher style, retribution is served as the Riley’s, are left in a car on a railway line, with a train fast approaching.