The Demon Headmaster Series by Gillian Cross

Dinah moves in with the Hunter family and starts going to the same school as her foster-brothers Lloyd and Harvey. It's not easy, as they seem to hate her, and school is really strange. Pupils suddenly talk like robots and do weird things - even Dinah finds herself acting oddly.She's sure the headmaster has some kind of power over them, and is determined to find out more. But the Demon Headmaster is equally determined to stop her.

Everyone at school is playing the new computer game, Octopus Dare - but only Dinah is good enough to beat it. As it begins to take hold, Dinah realizes that the game is trying to control her. But why is it happening, and how is the Demon Headmaster involved?

There's a new craze - Hunky Parker. Everyone's watching the TV programmes and queuing up to buy Hunky T-shirts, trainers like pigs' trotters and pig-swill yoghurt. Is it just normal hype or is something sinister going on? When there are riots Dinah and her friends start to investigate. But someone has a plan, and they're not going to let it be scuppered by a bunch of kids... moreThere's a new craze - Hunky Parker. Everyone's watching the TV programmes and queuing up to buy Hunky T-shirts, trainers like pigs' trotters and pig-swill yoghurt. Is it just normal hype or is something sinister going on? When there are riots Dinah and her friends start to investigate. But someone has a plan, and they're not going to let it be scuppered by a bunch of kids. BLGillian Cross has won the Carnegie Medal, the Whitbread Children's Novel Award, and the Smarties Prize, and is a highly-acclaimed author. Sales of her books exceed one million copies. less

The Demon Headmaster is in charge of a scientific research centre and has created an Evolution Accelerator: a machine to speed up the evolution process and produce the perfect human. But for this he needs Dinah's DNA, and then to put her into terrible danger to test his theories...This is the fourth title in the best-selling series which inspired the top-rating TV series.

All the knowledge in the world is being snatched away by the Green Hand organisation. When Dinah and SPLAT investigate, they discover the Hyperbrain, a machine with a controller who sounds horribly like the Demon Headmaster.