Prudence Bulstrode has fond memories of St Marianne's School for Girls, the beautiful Cornish school where she boarded as a girl. It was at St Marianne's that Prudence first learned the joy of cooking, from her dear old Home Economics teacher, Mrs Agatha Jubber. So when she's invited back to the school, to lead an Easter holidays course in the fundamentals of cookery, Prudence couldn't be more delighted. What's more, it's a chance to show her grand-daughter Suki the way school used to be in the good old days.
But no sooner has Prudence arrived at St Marianne's, a gruesome discovery is made. The builders excavating the old hockey pitch to construct the new dormitories have unearthed human bones - bones dating from Prudence's own time at St Marianne's. Soon, Prudence recollects the story of the vanishing schoolmaster, Mr Hubbard, and the rumours that spread like wildfire one summer about his illicit affair with Agatha Jubber.
So begins Prudence's very first cold case . . .