Willow Darby is on a family vacation for the first time in years. It's the 4th of July weekend on Mackinac Island and Main Street is teeming with tourists from all over the world. Moments before the last scheduled ferry is to arrive and return passengers to the mainland, the mistaken sounds of celebratory fireworks explode into screaming and chaos. Hannah and June Darby are missing. Willow must now rely on the one thing that no tactical training...