Something odd is happening after dark in Britain's schools... Ofsted, the schools' Inspectorate, are deeply worried. To lose one inspector in the line of duty might be considered a misfortune, but to have four inspectors lured into school after hours, dispatched, and left in outlandish poses before a cryptic message scrawled on the blackboard - that just looks like carelessness. Helen Haversham, Year 1 teacher at Hornby Infants School, is also worried. Both Ofsted and Christmas are coming. Her displays are up, her paperwork is done, and she has read the Head's memo explicitly forbidding ritual homicide, and yet something doesn't seem quite right... Who has been making midnight visits to the school? What has so unhinged the leader of the Ofsted team? How can she stop the class guinea pig from going on another dirty protest? If Helen can't answer these questions by Friday story time, then the school's end of term carol concert and Nativity is going to come to a truly unforgettable climax...