"I blame those new Brainy Crisps. Since he started eating them, he's been too clever by half."

Can eating a bag of crisps really make you more clever? The company that makes the crisps says so, and they seem to be right. But the Doctor is worried. Who would want to make people more brainy? And why?

With just his sonic screwdriver and a supermarket trolley full of crisps, the Doctor sets out to find the truth. The answer is scary — the Krillitanes are back on Earth, and everyone is at risk! Last time they took over a school.

This time they have hijacked the internet. Whatever they are up to, it's big and it's nasty. Only the Doctor can stop them — if he isn't already too late...