You have to go back 10 years to the time when Norman murdered his mother and her lover.
8 seconds sound clip from the Psycho (1960) movie soundboard.
You can hear this line at 01:43:47 in the Blu-ray version of the movie.
Quote context
[...]
- The private investigator, too.
- If you drag that swamp somewhere in the vicinity of the motel, you'll...
- Have you any unsolved missing persons cases on your books?
- You have to go back 10 years to the time when Norman murdered his mother and her lover.
- Now, he was already dangerously disturbed, had been ever since his father died.
- Then she met a man, and it seemed to Norman that she threw him over for this man.
- Now, that pushed him over the line and he killed them both.
[...]