"The Riddle of the Sphinx" is the third episode of the third series of the British dark comedy anthology television programme Inside No. 9. It first aired, on BBC Two, on 28 February 2017. The episode was written by the programme's creators, Steve Pemberton and Reece Shearsmith, and directed by Guillem Morales. "The Riddle of the Sphinx", which is set in Cambridge, stars Alexandra Roach as Nina, a young woman seeking answers to the Varsity cryptic crossword, Pemberton as Professor Nigel Squires, who pseudonymously sets the crossword using the name Sphinx, and Shearsmith as Dr Jacob Tyler, another Cambridge academic. The story begins with Nina surreptitiously entering Squires's rooms on a stormy night and being discovered; this leads to Squires teaching her how to decipher clues in cryptic