Older couple kidnaps young couple

I saw part of a movie years ago (over 15) while I was in Scotland on TV.  The film might have been in French.  It was color.  From what I remember an older couple had kidnaped a younger couple and took them to a rundown house or cottage.  Now either the older man seduces the younger girl into sleeping with him or it’s the older woman who seduces the younger guy.  This then leads to the other pair sleeping together.

That’s all I remember.  Thank you.

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