Oliver loves mountain biking on rocky, wooded trails. And he has an unlikely partner—his much older half sister Morgan. One summer evening while out with their dog Digby, Oliver tries to impress Morgan by leading her down a new trail he claims to know. They end up at the bottom of a canyon with no choice but to push their bikes up the steep trail. Then disaster strikes. Morgan slips and badly injures her ankle. With no cell service, it's up to Oliver to hike out and get help. But daylight is fading fast, and danger waits in the wilderness.