Eccentric inventor Professor Branestawm fights the forces of evil in this comedy adventure film, based on Norman Hunter's iconic children's books. Armed with a multitude of crazy inventions, and alongside his eccentric allies Colonel Dedshott, Mrs Flittersnoop and young apprentice Connie, Branestawm, the original mad professor, takes on scheming businessman Mr Bullimore and officious local councillor Harold Haggerstone, to try and stop their plans to bulldoze his workshop to make way for a giant munitions factory, right in the middle of town.

When Lady Pagwell dies, leaving a substantial sum to fund local inventing, it could mean the end of Professor Branestawm's money troubles. But scheming local councillor Harold Haggerstone will stop at nothing to thwart Branestawm and insists that Pagwell holds an inventing competition to decide who gets the money. Haggerstone tries to hire his own rival inventor. Professor Mary Oxford, from Cambridge, fails to impress with a nuclear powered paperweight. The Invisibaliser presented by Professor Awfulshirt causes havoc (and much invisibleness). But when Professor Algebrain, from an unspecified European country, turns up, Haggerstone thinks he's onto a winner. Branestawm, meanwhile, is having problems of his own. Not only is he struggling to come up with an invention that will really knocks the judges' socks off, he's upset his faithful young assistant, Connie. He's so wrapped up in his work that he's been neglecting her, and she's torn between helping him and working with the seemingly charming and attentive Professor Algebrain.