All That is Buried — Robert Scragg

A parent's worst fear is realised when seven-year-old Libby Hallforth goes missing at a funfair; no witnesses, no leads, and no trace. Months later, after the trail for Libby has gone cold, DI Jake Porter and DS Nick Styles find human remains but that's just the tip of a gruesome iceberg. Everyone is a suspect, nobody can be trusted, including the Hallforth family. The chances of getting justice for Libby are fading fast, along with Porter's chances of stopping a killer before they strike again.