Something is killing the children

"When the children of Archer's Peak--a sleepy town in the heart of America--begin to go missing, everything seems hopeless. Most children never return, but the ones that do have terrible stories--impossible details of terrifying creatures that live in the shadows. Their only hope of finding and eliminating the threat is the arrival of a mysterious stranger, one who believes the children and claims to be the only one who sees what they can see. Her name is Erica Slaughter. She kills monsters. That is all she does, and she bears the cost because it must be done"-- Provided by publisher