One day, as Cara and her siblings are trying to clean up the canal where they live, they pull out a mysterious locked safe. Though none of them can open it, they're sure it's something special. That night, a thief comes after the safe. The children flee, travelling with their boat as far as they can, before continuing into the forest on foot. But soon they're lost in the mountains with a snowstorm about to land and food supplies running low. Will Cara and her siblings be able to survive the wilderness with nothing but their wits, their bravery and one very large dog to help?