Sandra and Charles Durro defied the odds and found love a second time. Together, they're raising their high schooler Ayla and enjoying part time duties with their grandson Michael. Sandra continues operating Simply Splendid Proposals while volunteering at Michael's preschool inside the church she's attended since Preston was little, while Charles steps in as head of Cruz Development. Life is complete; life is wonderful. That is until Sandra hurts her back at the preschool and meets Victoria's chiropractor—the sexy, promiscuous, and troubled Isabelle.

Isabelle seamlessly infiltrates the Durros' lives and invites them to join her at her favorite late-night spot Secret Sins. In this place, successful Miami couples fulfill their wildest sexual desires. When Sandra and Charles reject Isabelle's physical advances and her bold offer to join them in their bedroom, things quickly derail. And when Isabelle realizes she can't have the Durros, she'll stop at nothing to destroy their healthy, loving marriage by tearing their lives apart.

Marriage Killer is a seductive, sexy thriller that will leave even the most stable couples wondering if something—or someone—could be strong enough to come between them.