Doctor is Serial Killer

by Gaillie
(Scotland)

I am trying to find the name of a film I watched in the late 70's or early 80's.

It starts off with a young girl taking a short cut through a field whilst listening to the radio. Next she is being chased by someone unknown.

This person is murdering young women and one of them survives but ends up in a clinic/hospital where she is in a sort of vegetative state - alive, but unable to recognize anyone or communicate.

It turns out it was the doctor who was treating her and looking after her that was the killer.

Can anyone please help me to find out the name of this film?