Long ago, in faraway Mesotpotamia, a faithful dog and Tobias, his young master, set out to cross the mountains. Tobias is on an errand to collect some money for his father, and it will also be safer for him if he stays out of town for a while. Little do they know what dangers are lurking as the two of them travel onwards, accompanied by their mysterious guide. Who is this guide? Tag, the dog, tells the story of their exciting adventures. Like all dogs, he is interested in smells. But unlike many dogs, he has to discover the worst smell of all: a demon.