Skating on the edge : [a mystery]

It's Native American Summer Days in Indian Falls, and Rebecca Robbins is roped into taking a turn in the Senior Center dunk tank. That is, until her rhinestone-studded grandfather Pop needs help setting up his Elvis act. Minutes from climbing into the tank, Rebecca has to find a replacement. Roller derby girl Sherlene-n-Mean takes her place, and is promptly electrocuted and killed. It's obvious to the police and Rebecca that this was no accident,...