This short story is set in the picturesque Catalan region of the South of France, and centres around Professor Jacqueline Mouchot, a French forensic anthropologist and American Professor Peter Phillips.
The couple are out exploring the area and decide to visit the small chapel of Notre Dame de la Salette. This particular chapel remains closed to the public except for the annual Harvest Mass, but knowing the keyholder of the only key to the chapel, they are permitted access.
However, as soon as they open the old door to the chapel, they know something is wrong because of the stench coming from within. It transpires that there are two dead bodies inside, a young couple, who have been missing since the previous spring.
From the injuries visible it is quickly determined that the man and woman have been murdered, but the chapel only had one exit, which was locked, and two windows which were sealed shut. And of course, there is only the one key to the door.
Who killed the couple, and why? What were they doing in the church in the first? And how did they – and the murderer – get inside if there was only the one key?
What unravels is a complex web of secrets going back years, all of which are suddenly brought into the light of day.