All her life, prodigy inventor Lucy has dreamed of having a grandfather who will take care of her, bake cakes for her, and make her hot chocolate with whipped cream. But when long-lost Grandfather von Humbug finally turns up, Lucy soon realises that he isn’t like other grandfathers: he’s an inventor and a vagabond, and above all, he loves earning easy money, no matter what it costs.

Catastrophe looms when Grandfather and his new girlfriend Vanessa Jones get their mitts on Lucy’s latest invention, a miracle powder.