Wer Im Glashaus Liebt (Der Graben) on AllMovie

Igor has a good job as an advertising manager, a nice house, his wife Hanna, and a mistress. He has invited Christine, the mistress, over to his house while his wife is away. They are deeply involved in the act of making love when his wife, who has returned early, discovers them. Igor desists, and makes ironic little comments about the situation. Hanna is not amused. She takes a gun, points it at him, and tells him to resume making love to Christine.