Grizzly cubs are disappearing from Glacier National Park, and the Landon family must figure out why! But for Jack, the real mystery is his sister Ashley's strange behavior. What was she doing alone in the woods so early in the morning? And why did she lie to their parents? Jack's efforts to unravel the truth lead to a pulse-pounding adventure that brings the Landon kids face to face with an enraged grizzly—as Jack and his sister suddenly become the hunted.