At the end, even as it is pouring rain, when Morse and Thursday make a go to the car, it is quite sunny by the long shadow they both cast.
When Dr. De Bryn is describing the heavy drinking of the murder victim, he refers to him sarcastically as "the last of the red-hot livers", a pun on the title of Neil Simon's well-known play, "The Last Of The Red-Hot Lovers". However, this episode of "Endeavour" is set in mid-1967, and Simon's play did not open on Broadway until December of 1969.