Which episode was this?

Hi there,

I'm trying to put a title to an episode of this series, but I haven't been able to so far. I can only remember three scenes but at 13-14 they were very disturbing, particularly the last two. I'm hoping someone will be able to recognise them and name that episode.

I believe a man went to a house that was owned or lived in by two sisters, a blonde and one with dark hair. The man began a love affair with the blonde. The dark haired sister was portrayed as rather mad.

The first scene I recall is when the man wakes up to find he has got razor blade cuts on his wrists that had been done by someone, and the assumption was it was the dark haired sister.

The next scene is towards the end and the man is shown at the bottom of some cellar stairs with similar razor blade cuts all over him, he was naked as I recall. The look on his face that the camera showed from the top of the stairs was something that stayed with me ever since.

As I don't want to spoil it for anyone, I just say the last scene I recall is of the perpetrater being taken away by the cops and they're laughing. It was this that really disturbed me.

You might wonder why after all these years why I'd want to stir up such a terrifying memory, well I guess to bury a ghost perhaps, I dunno.

Many thanks for any help on this
Colin