Acting on a mysterious tip-off, Brunswick goes under cover as a careers master in a prestigious girls' school. An eminent former pupil who has been invited to open a new science block is also a criminal mastermind.

Inspector Steine receives a breathless phone call from a mysterious lady, calling from a famous girls' school on the edge of town. A rich old girl has donated a new science block. This rich old girl is the most successful criminal mastermind in the south east: in short, she is Mrs Groynes!

Brunswick goes undercover (and very nearly underwater), Twitten behaves like a teddy boy at Rock Around the Clock, the standard of schoolgirl pickpocketing skills takes the breath away, and Mrs Vine adds another broken heart to her collection.

With Nicholas Le Prevost as the headmaster (You girls!), Michelle Tate as Phyllis, and Janet Ellis as the evil Mrs Adelaide Vine.