1930. When a body is discovered on the premises of the newly-established Maxstead Court School for Girls, Detective Inspector Herbert Reardon is called in to investigate. His wife Ellen having just accepted a job as French teacher, Reardon is alarmed to find the school a hotbed of scandalous secrets, suppressed passions, petty jealousies and wanton schoolgirl cruelty. As he pursues his enquiries, it becomes clear that the dead woman was not who - or what - she claimed to be. Who was she really - and why is Reardon convinced that more than one member of staff is not telling him the whole truth? Then a pupil goes missing - and the case takes a disturbing new twist...