1792. Louis XVI, his wife Marie Antoinette, and their children have been arrested and imprisoned in the Tour du Temple, a sinister chateau in Paris, awaiting their trial. Far from the splendour of Versailles, they are isolated and vulnerable for the first time in their lives.

In 1956 France, a priest is violently murdered, and Sister Irene begins to investigate. She once again comes face-to-face with a powerful evil.