The two thirtysomething British 'girls' happily live at home with their wealthy parents, and resent the frequent houseguests their parents invite to stay. At present, the guests are Father Snow, a priest mourning the death of his lover, and Arleen, a dowdy American woman who is a friend and advisor to Father Snow. The girls delight in reading Arleen's diary and mocking her, both privately and openly. To their parents they are sickly-sweet, but they love to humiliate these guests in their parents' presence. When Father Snow and Arleen gift their parents with a cocktail shaker, the girls open a kitchen cupboard to show them that the family already owns ten cocktail shakers. They make fun of Father's Snow's grief, having never been in love themselves, and with no intention of ever being in love, as they are perfectly happy with each other and the advantages of home. The girls do however worry about their parents, who seem to be ageing and growing depressed, though the girls can't imagine why. The girls' mother tells them that Arleen saw their cats playing cruelly with a mockingbird. The girls insist their cats would never do any such thing, though they have themselves witnessed at least a dozen birds slaughtered by the cats, and have admired this violence with glee. The girls are outraged when, after catching them reading her diary, Arleen reveals their mother confides her dreams to her. At dinner that night, after mocking Father Snow's dead partner, the girls ask their mother to tell the story of the night their father proposed. Mother doesn't tell the full story, so the girls deliver it: on the way to the proposal, their father had struck and probably killed someone on the highway, but had not stopped as he didn't want the incident to disrupt his bright future. This story clearly shocks Father Snow. Mother asks him if there is any way to make amends, and Father Snow talks about the inadequacy of repenting. Father is unrepentant anyway. The cats arrive and Arleen plucks a couple of bloodsucking ticks from them, which the girls refuse to believe came from their darling cats at all. They accuse Arleen of being a magician. Father Snow says she is one of the most decisive judges of character he's ever met. The clearsighted Arleen tells Mother that she should get rid of the girls, and that they are slowly killing her. Shocked, Mother keels over dead from a stroke, and Father Snow, finally shaking off his grief, gets up to help.