He Was Not There — P.D. Workman

Zachary Goldman just wants to put everything that happened to him that night at the hands of a monster behind him forever. But when Heather, his estranged sister, asks for his help in bringing her own rapist to justice, there is no way he can turn her down. 

The case is cold, three decades ago. Heather never saw her attacker's face, as he was wearing a mask. At the time, the police did everything they could, but there have been new advancements in technology and Zachary hopes to turn up something he can use to solve the case. 

Somehow, he needs to find a way to finally bring Heather some peace, even when it means dealing with his own painful memories.