The Final Problem
Season 1 (October 2, 1939 – March 11, 1940; 24 episodes) started with an adaptation of "The Adventure of the Sussex Vampire" and ended with an adaptation of "The Adventure of the Retired Colourman". The last episode of the season was originally intended to be an adaptation of "The Final Problem". It is not known why the change was made, but it may be because "The Final Problem" had already been used on radio several times. It was announced on the penultimate show that "The Final Problem" would be the last episode; in the final episode, Watson said he had changed his mind about which story he was going to tell.