Premise: Agatha Christie's Marple (or simply Marple) is a British ITV television series loosely based on the books and short stories by British crime novelist Agatha Christie. The title character was played by Geraldine McEwan from the first to third series, until her retirement from the role, and by Julia McKenzie from the fourth series onwards.
Hypothesis: Geraldine McEwan played the title character for only 2 series.