At one point, Professor Gold (Anna Massey) asks Lewis if they have ever met before. She then says that Lewis was working with Morse. Anna Massey played the character of Lady Emily Balcombe in the Morse episode 'Happy Families (1992).'
The music played by the string group in the concert that Lewis attends with his boss is String Quartet No 12 in C minor by Franz Schubert.
The only episode of Lewis that opens with a pop song: "The Seeker" by The Who. The same song is used on the trailer for the 2016 season of "Endeavour," which is a spin-off of--and a prequel to--"Morse."
Following the events of the pilot episode--with Lewis returning and being teamed up with Hathaway--Lewis and Hathaway are an established partnership from this episode onwards.