Showing China Lake by Meg Gardiner

Evan Delaney is a heroine of our times: a woman with a big heart, a quick tongue and a hot temper that get her into trouble. She is shocked to discover that Tabitha, her ex-sister-in-law, has joined the Remnant - the Reverend Peter Wyoming's fanatical band of disciples. And that Tabitha is trying to regain custody of her six-year-old son, Luke, currently in Evan's care, while his father is posted to the Naval Air Warfare Center. Then, one of the Remnant is killed, and Evan's brother is the prime suspect. With her boyfriend, lawyer Jesse Blackburn, Evan tries to clear her brother's name and rescue her nephew. In doing so, she finds herself caught up in a wild plan to steal weapons, and a blazing inferno on a Santa Barbara hillside.