Prudence Bulstrode has fond memories of St Marianne's School for Girls the beautiful Cornish school where she boarded as a girl. 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 . . .