Jason Rafiel dies in the first few minutes of the film but later turns up played by another actor in another Joan Hickson Miss Marple - but the book it's based on was written before Nemesis, so only filmed in the wrong order.
In Greek mythology, Nemesis is a sister of Lachesis, Clothos, and Atropos, the Three Fates, whose names are reflected in those of the three Bradbury-Scott sisters -- Lavinia, Clothilde, and Anthea.
Jason Rafiel: It's up to her now. Thousand of years ago she had a measuring rod, a sword, and a whip. Yes, it was called a scourge. She rode about in a chariot drawn by griffins. Nemesis. Last time I saw her, she was wearing a pink, woolly shawl.