The Collector (1965)

 The Collector (1965)

The Collector refers to a lonely butterfly collector played by Terrence Stamp, who lives by himself in rural England. He kidnaps a pretty college student played by Samantha Eggar. He has no plans to hurt her but feels that the more time she spends with him, the more chances she will fall in love with him

That backstory is the major difference between "The Collector" and your other serial killer movies. Today's serial killer movies starts with the mad killer. The Collector starts out fairly innocently and slowly loses that sense of kindness. The movie's end is almost the opening of today's murderer movies. (IMDB - strokeguy)