 Episodes run for either approximately 50 minutes or 90–100 minutes, the latter of which is the format of all episodes from series 6 onwards.The shorter episodes are based on Christie's short stories featuring Poirot, many published in the 1920s, and are considerably embellished from their original form.The longer episodes are based on Christie's 33 Poirot novels and one short story collection ("The Labours of Hercules").