In the TV movie that led to the series, Morse is seconded from the Carshall Newtown police force to Oxford to investigate the murder of a 15-year-old girl. In the end, Morse decides to transfer to Oxford full-time. Morse’s new landlady tells him that the other two lodgers are named Goldberg and McCann. Carshall New Town (or Newtown as it is spelled here) is the setting of Angus Wilson’s novel Late Call, while Goldberg and McCann are from Harold Pinter’s play The Birthday Party. Both the movie and Series 1 take place in 1965.
In the second episode of Series 1, "Fugue," Morse attempts to apprehend a serial killer whose methods are based on the deaths of characters in various operas. Chief Superintendent Bright calls in Dr. Daniel Cronyn, an expert on serial murders, as a consultant on the case. Cronyn refers to killings in the States in the last ten years: the Starkweather case, the bodies in the swamp at Fairvale, and DeSalvo in Boston. The bodies in the swamp at Fairvale are a reference to Alfred Hitchcock’s film Psycho, based on Robert Bloch’s novel of the same name. Since Psycho takes place in the CU via a reference in Christopher Farnsworth’s novel Red, White and Blood, we have the first piece of evidence that Endeavour is as well.
In the third episode, "Rocket," Morse looks into the death of a worker at a munitions factory owned by the Broom family, which occurred during a visit by Princess Margaret. The factory’s union shop steward is Reg Tracepurcel. The youngest Broom, Johnny, boasts to Morse that his car is the new Bellini. The Bellini is a fictional brand of car driven by Raymond Delauney in the 1960 film School for Scoundrels. Some elements of this episode’s plot reference the British film I’m All Right Jack, which featured a character named Bertram Tracepurcel. Perhaps Bertram and Reg are related. I’m All Right Jack starred Terry-Thomas, who also played Raymond Delauney in School for Scoundrels. The plot is also heavily influenced by the movie The Lion in Winter, but none of the references to that film count as crossovers.
The fourth and final episode of Series 1 is "Home," in which Morse investigates the hit-and-run killing of an Oxford don. One of the suspects in the case is retired gangster Vic Kasper, who is now persona non grata with Sid and Gerald Fletcher. Later, one of Vic’s employees tells the ex-criminal’s son Vince (who is secretly in a partnership with the Fletchers on a construction deal) that Thorpey is on the phone. Gangsters Sid and Gerald Fletcher are Jack Carter’s bosses in the 1971 film Get Carter. One of the gangsters in Get Carter is named Thorpe (also referred to as “Thorpey”), and is an old acquaintance of Jack’s. Thorpe must have worked for the Fletcher brothers for a time before switching his loyalties to rival crime boss Cyril Kinnear.