The Alfred Hitchcock Hour (1962)

S1E2 Don't Look Behind You

On a college campus, two young girls are murdered during a walk in the nearby woods. Suspicion quickly turns to a chemistry professor and the dark, brooding music professor, Edwin Volck. Harold, a psychology professor, persuades his fiancée Daphne to pose as bait to capture the killer. Their plan works, exposing Volck as the murderer. However, Harold grows anxious, fearing that Volck's violent tendencies may have awakened other potential psychopaths on campus. As Harold's own dark thoughts take shape, he unexpectedly attacks Daphne, but she is saved by the chemistry professor, who had been monitoring Harold's unsettling behavior all along.