Courage Mountain : The Further Adventures of Heidi Book

Heidi (of the goats and the saintly ways and curmudgeony-but-secretly-loving grandfather) is a teenager living far from the Swiss Alps of Heidi. But when Nazis come for her young charges, she and her old friend Peter set off on a dangerous trek across a barren landscape to reach the safety of her former mountain home.

This book is probably why I am still, to this day, intensely afraid of frostbite. Nowhere near as engaging as the original story of Heidi, but I'm a sucker for adventures about strong-principled girls who accomplish incredible acts of physical courage.