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
Cindy Valentine and "Laverne & Shirley"), and her hit single "Pickup The Pieces (To My Heart)" appears in the film "" (1991). For much of the 1990s into 2003, Valentine worked behind the scenes in film and television, as a composer and musician. Composer Dominic Messinger and Valentine teamed in 1997, with credited works for the sequel to Mickey Rourke's "Another 9 1/2 Weeks", and the television series "As the World Turns" and "Sirens". Since 2000, Valentine has involved herself with horror, documentary and art genre films, such as the critically acclaimed "" (2008) and is credited as Producer on "Ruth" (2000)