Право Права первой ночи / Droit de cuissage, Le (1980)

This is a terrific film, one of the best French ones of its period, which is saying something.

Plot - a man has friends who enjoy group sex, but his wife refuses to join in. With the complicity of the husband, she is seduced by one of the friends, who arouses her desires and initiates her into practises she will not allow her husband. After a series of sexual encounters she is eventually up for anything. Wife well acted as someone passive but carried away by the intensity of her desires. Bit part by Serena, actress unique in ability to convey relish in all she does. Sex well acted a\d and edited, various.