Kate Moore is the protagonist of The Expats. The narrative is exclusively filtered through her perspective, allowing the reader to understand the actions and motivations of the characters around her as she comes to realize them. Kate is a retired analyst for the CIA, though she previously worked as a field agent assigned to liaise with foreign leaders across Latin America. In most cases, her objectives ensured that these countries would cooperate with the US agenda for continental development, though sometimes this would force her to commit acts of espionage, intrusion, and—in some cases—murder. These skills become useful to her in her post-career life once she realizes that her husband, Dexter, and her new friends, Bill and Julia Maclean, may be involved in questionable business.

Kate entered the CIA immediately after finishing college. She believed that she could not form substantial attachments with anyone, owing to the untimely death of her parents and her estrangement from her only living relative, a sister with a drug and alcohol addiction. This assumption changed when Kate met Dexter. Their romance resulted in marriage, and they went on to have two children named Jake and Ben.