The Riddle of the Sphinx (Inside No. 9) was characterised by Pemberton as a thriller in the style of Anthony Shaffer's 1970 play "Sleuth", while Shearsmith identified the episode as particularly theatrical, in the style of "Sleuth" and Ira Levin's 1978 play "Deathtrap". BBC executives, according to Shearsmith, saw the episode as a cross between "Sleuth" and Willy Russell's 1980 play "Educating Rita" that read as if it had been authored by psychopaths. The executive producer Jon Plowman suggested that the first half of the episode plays out like a radio play. The word-play and tea-drinking in this part of the episode are, in the writers' opinion, very
Chico and Rita gig in Paris and a European tour. Rita becomes a big film star while Chico finds a new girlfriend in Paris. One morning, while playing "Rita" at the piano, the girlfriend's dog, Lily, comes in and sits by Chico. He decides to change the name of the song to "Lily". Back in New York, despite her wealth and success, Rita is still mistreated socially due to her skin color. While being driven to a set, the radio plays a new Jazz hit that she instantly recognizes as the piece Chico composed for her. She is moved to tears when she