White Heat by Brenda Novak

A dangerous cult has recently taken over the desert ghost town of Paradise, Arizona. Members worship at the feet — and in the bed — of its charismatic leader, Ethan Wycliff, and obey his orders blindly. They’ve already tried to murder one woman and they’re implicated in the disappearance of another.

Nate Ferrentino, who works for private security contractor Department 6, has been assigned to infiltrate this group. It’s a challenge he welcomes — until he learns that colleague Rachel Jessop will be going undercover with him. Thanks to their shared history, he’d much rather go alone...

The problem is, only married couples can participate in cult rituals. So, like it or not — and they don’t — Rachel and Nate must pretend to be husband and wife.

There’s no choice. Because if Wycliff isn’t exposed, if he isn’t stopped, more people will die. And Rachel might be one of them.