A quiet Ohio suburb is shattered when a 17-year-old girl, Mackenzie Shirilla, drives nearly 100 miles per hour into a brick wall, killing her boyfriend and a close friend while somehow surviving herself. Was it a tragic accident, a medical emergency, or a carefully calculated act of murder? This week, we examine the evidence, the trial, the toxic relationship at the center of it all, and the questions that continue to divide people over the case.