Mr. Melton is manager of the Lost Caverns Hotel and the main villain of the movie Abbott and Costello Meet the Killer, Boris Karloff. Despite the movie's title, he is the killer, not Boris Karloff's character.
The movie takes place in a California hotel where a prominent lawyer named Amos Strickland is murdered. Due to empty threats made by Freddy (Costello) after Strickland caused him to lose his job, as well as Melton's accusations, Freddy soon becomes the number one suspect. After a pair of detectives place Freddy under house arrest, more dead bodies and incriminating evidence are planted in his hotel room, and a menacing swami (Boris Karloff) tries unsuccessfully to hypnotize him into killing himself.
Just as Freddie is about to be arrested for the murders, a voice from an air duct instructs him to come to the nearby caverns with a bloodstained hankerchef. There, he meets a masked figure who tries to drown him after he reveals that he burned the hankerchef, but the detectives rescue him. Later, back at the hotel, Melton is revealed to be the killer after he is found with muddy shoes from the cavern. He tries to escape, but is caught in a booby trap set by Freddie and arrested.