The Mistletoe Mystery opens with the revelation that Euphemia is writing for her daughter! It's Christmas tide and Euphemia is again working for Bertram at his ill-fated estate in the Fens, White Orchards. Bertram's sudden desire for a big Christmas house party creates a huge task for Euphemia and one in which her normally excellent staff are reluctant to take part. As she struggles with her responsibilities Euphemia learns that White Orchards is built on the site of Hadwell House, a manor that suffered a terrible fate one Christmas Eve. As Christmas draws closer, people start behaving strangely, Euphemia is having nightmares and there is a palpable sense in the air that something is very wrong. Forming an unlikely alliance with Bertram's step-sister Richenda, Euphemia tries to prevent disaster befalling the entire household and faces her most terrifying mystery as she sets herself against seeming supernatural forces.