Twelve by Jennifer Lynn Barnes

Cassie Hobbes has been working with the FBI since she was a teenager. Now twenty-three years old, she and her fellow Naturals have taken over running the program that taught them everything they know. As a unit, they're responsible for identifying new Naturals--and solving particularly impossible cases. When their latest case brings back a ghost from their past, Cassie and the other Naturals find themselves racing against the clock--and reliving their own childhood traumas.In a small, coastal town in Maine, there has been a rash of teen suicides--or at least, that's what the police believe. Mackenzie McBride, age twelve, thinks differently. Desperate to make herself heard, she stands at the top of a lighthouse, threatening to jump... unless the FBI agents who rescued her from a kidnapper at age six come to hear her out.Enter the Naturals. It doesn't take Cassie long to realize that Mackenzie isn't bluffing: she truly is convinced that the suicides are murder, and she really will jump if she can't get the FBI to believe her. To the outside world, Mackenzie is nothing more than a traumatized child. But so was Cassie, once upon a time. So were Michael, Dean, Sloane, Lia, and Celine. With a storm rolling in off the ocean and Mackenzie's position becoming more precarious by the moment, the Naturals have very little time to get to the truth about the deaths--and about twelve-year-old Mackenzie McBride.