Opal. GEM Series, #1

When Opal goes undercover in a youth center several teenagers have disappeared from, she's shocked to find a ghost of her own traumatic past at the helm. However, her worry for the missing kids is greater than her concern being recognized and she risks her own safety to discover the truth.  To complicate matters, a familiar FBI agent shows up conducting his own investigation and almost blows the whistle on her.
It takes some doing to convince him to join forces with her but as it turns out, they work well together.  In the course of uncovering an organized group of child molesters, they find themselves falling-for each other.