Summary from GoodReads:

The most riveting novel yet in Christopher Reich’s New York Times bestselling series—featuring Dr. Jonathan Ransom and his undercover-agent wife Emma, a dangerous woman with a mysterious past who has gone rogue in the high-stakes, serpentine world of international spies.

In 1980, a secret American B-52 crashes high in a remote mountain range on the Pakistan–Afghanistan border. Nearly thirty years later, and spanning locales from those peaks to New York City, a terrible truth will be revealed.

Jonathan Ransom returns as the resourceful doctor thrown into a shadowy world of double and triple agents where absolutely no one can be trusted. To stay alive, Ransom must unravel the mystery surrounding his wife—an enigmatic and lethal spy who plays by her own rules—and discover where her loyalties truly lie.

Rules of Betrayal is a masterfully plotted novel that cements Christopher Reich’s reputation as one of the most admired espionage thriller writers today.