When a prize-winning essay earns Laura Marlin an invitation to a midnight picnic on mysterious Bodmin Moor she can hardly wait, especially since her best friend, Tariq, and husky, Skye, get to come too.

But Bodmin is a place steeped in legend and as the fog descends it becomes hard to separate myth from reality. When a freak accident leaves the children alone, Laura has to use all her powers of deduction to outwit an enemy who may not even exist.