Zack Mosel's mum and dad are away in far-off Slovodnia, so Zack has no choice but to spend his summer holidays with 'Mag the Hag', his eccentric grandmother.

But before the summer can get too boring, Zack finds out his parents have gone missing, and he and Mag take it into their own hands to unravel the mystery surrounding his parents' disappearance. As Mag and Zack trek across Europe, they face wilderness, danger, new friends, enemies and excitement ... all while traveling on the seat of an extraordinary motorbike.