Inside Amy (1974)

Charlie, a well to do suburbanite lawyer, and his beautiful loving wife Amy have been married for 10 years. He is so bored with his perfect life, so he suggests to her that they go to a swingers party. After a little convincing she agrees, but things don't go as well as poor Charlie had hoped once they get to the party. She's having a great time, all the guys are into her. He on the other hand is having a bit of trouble rising to the occasion. Soon after the party, he launches into a jealous murder spree and begins slaughtering anyone who has or wants to sleep with his wife.