Three of the Brains have disappeared, along with Ian. Dinah begins to catch on to what is happening, and everything depends on SPLAT getting to her. Then there's the matter of the booby trap to consider.

SPLAT have found a way in to Vulcan Tower, and the Computer Director is using mind control, but Dinah doesn't understand why - yet.

The latest craze is 'octopus dare' and junior computer brain of the year competition. Dinah is a natural contender, but her behaviour becomes very odd. Could it be that the evil headmaster is up to his new tricks in a bid to take over the world?

The Demon Headmaster's plans for Dinah are discovered - and SPLAT forms a counter-plan.

The boys get suspicious of Dinah's state of mind when she breaks one of the headmaster's rules. Based on Gillian Cross's books.

As Lloyd and Harvey await the arrival of their new foster sister, they wonder if she will be able to resist the mysterious powers of their sinister headmaster. Based on the books of Gillian Cross.