Mastermind of Mayhem

Adam's parents run a holiday park by the sea. It's mostly quite a quiet life, until his friends come to stay for the summer and they discover that Professor Goodspeed, the old man who's just moved into the big house on the cliff, can make gadgets like flying bikes and pens that shoot darts. Turns out, he used to work for MI6. After the kids accidentally reveal his location to the whole world, the quiet seaside town becomes a hub of international villainous activity. When the Professor is kidnapped, they have to find him before the dastardly Dr Toe uses his gadgets to take over the world.