Hannah Plum and Patti Woo are staying in a creepy, rundown chalet in the Shadow Mountains National Park, where Patti's aunt Unjoo works as a ranger. The girls' parents are keen to spot an ice owl there, but soon, they're all out looking for Unjoo's stolen dog instead. The only clue is a bit of silver wool on a kennel, and Plum & Woo sense the markings of a crime.

With rumors of a terrifying silver wolf snapping at their heels, the girls investigate - at their peril. Who's trying to push them off a ski slope? Is something wicked hiding in the woods? Could a silver scarf be the key to the dog's disappearance? And is Hannah's new friend - from the local lolly shop - really as sweet as he looks?

Hannah and Patti will need to keep their fur-trimmed boots fastened if they're going to survive this chilling bird-watching holiday. And that's if they can survive the woods (and each other) first ...