Longing for Sin by Kennedy Layne

Brooklyn Sloane has left her job as a consultant for the FBI to take on her first cold case in the private sector. Doing so allows her the freedom to work the one case she’s never professionally been allowed to touch – a ruthless serial killer, who just so happens to be her own brother.
Privately, she’s hunting her only sibling, but alongside her team, she’s seeking justice for those without a voice. But there is always the anomaly…
Seven arrests. Seven trials. Seven closed cases.
Brook has discovered one thread that ties them all together. Soon, as the investigation begins to unravel, the evidence all points to one disturbing truth – the real serial killer has never stopped hunting innocent victims, planting evidence, and causing others to pay for his violent crimes. Unfortunately, he isn’t Brook’s only concern. As she divulges deeper into her brother’s reign of torment, she finds herself falling down a dark rabbit hole where she lands on a web of deceit. Who wins is unknown, for their chilling lies can make for very convincing truths.