Roses of May (The Collector, #2) by Dot Hutchison

Four months after the explosion at the Garden, a place where young women known as the Butterflies were kept captive, FBI agents Brandon Eddison, Victor Hanoverian, and Mercedes Ramirez are still entrenched in the aftermath, helping survivors in the process of adjusting to life on the outside. With winter coming to an end, the Butterflies have longer, warmer days of healing ahead. But for the agents, the impending thaw means one gruesome thing: a chilling guarantee that somewhere in the country, another young woman will turn up dead in a church with her throat slit and her body surrounded by flowers.

Priya Sravasti’s sister fell victim to the killer years ago. Now she and her mother move every few months, hoping for a new beginning. But when she ends up in the madman’s crosshairs, the hunt takes on new urgency. Only with Priya’s help can the killer be found—but will her desperate hope for closure compel her to put her very life on the line?