Plot synopsis: In London, Tom and Phyl are self-assured and in control of the situation whenever they meet their friends Huw and Tegwen. But when they're not on home ground and when they accept an invitation to visit Huw and Tegwen’s home in Wales, relationships change more than a little Huw, a London barrister, whose heart is in the Welsh hills, is truly king of his castle, and shocks and excites Phul with some of his "Cassanova" qualities. And Tegwen's relationship with her husband intrigues Tom, whose marriage is more of an easy companionship. But why have they been invited for the weekend?