It's summer and all of Ulrik's school friends seem to be going on something called "vacation," so Mr. and Mrs. Troll decide to investigate. Their neighbors, the Priddles, have just bought a camper, and it seems the Troll family has been invited to join them. When they arrive at the campsite and the Priddles open the camper to discover it full of trolls, they don't seem very pleased. But this is the least of their worries, as stories of a wild, sheep-devouring Beast on the loose near their campsite start to surface, and Ulrik finds himself helping to solve a hairy, scary local mystery.