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.

The headmaster turns to genetic engineering to gain revenge over Dinah.

Rose embarks on her plan to drive a wedge between Dinah and her adopted brothers. Based on 'The Demon Headmaster Strikes Again' by Gillian Cross.