Blood on my hands

Callie is at an October keg party in the woods, when she notices that her friend Katherine has gone missing. The kids spread out to look for her and Callie finds her, lying on a path, with a big, bloody fake knife in her. She reaches for the knife and raises it, only to discover, to her horror, that it is real. At that moment, another of the search party stumbles on them, and takes a photo of Callie holding the bloody knife. Now she is the suspect in a grisly murder. How can she prove her innocence – and find the true murderer?