In August of 2017, Will Grenier, his younger sister Cassie and their friend Erin Gibbs were headed up the Middle Teton. They were all experienced hikers. At the time, 24 year old Cassie worked as a recreational therapist and her job involved taking kids with troubled backgrounds into the great outdoors. Going up the Middle Teton was supposed to be a day off, but as they scrambled up a talus slope a massive rock slide cut loose and Cassie was right below it. What should have been a typical day hiking in the park turned into a fight for survival.