Theres no police training stronger than a cops instinct. Faith Mitchells mother isnt answering her phone. Her front door is open. Theres a bloodstain above the knob. Everything Faith learned in the academy goes out the window when she charges into her mothers house, gun drawn. She sees a man dead in the laundry room, a hostage situation in the bedroom. What she doesnt see is her mother. When the hostage situation turns deadly, Faith is left with too many questions. Shell need the help of her partner, Will Trent, and trauma doctor Sara Linton to get some answers. But Faith isnt just a cop anymore, shes a witnessand a suspect. To find her mother, Faith will have to cross the thin blue line and bring the truth to lightor bury it forever.