Middle-aged Kath, dressing far younger than her years, lives in a Gothic building next to a graveyard, with her father, Kemp - 'the Dadda'. One day she sees an attractive young man sunbathing on one of the tombstones. Eyeing him greedily, she offers to rent him a room, after he explains he is a homeless orphan, visiting his parents' graves.

Kath tells Sloane that she was once married, and had a son who died, but then admits that the child was illegitimate and she gave him away. She keeps mementos of the child's father. She tells Sloane that she will be his new mummy and he will be her new son.

Kath has a brother, Ed. Kemp has not spoken to him for twenty years, ever since he caught him committing a "felony" in the bedroom. Kemp thinks he recognises Sloane, suspects him of murder and attacks him in the leg with a garden fork. Kath tends the wound, getting Sloane to remove his trousers while telling him that she had an upbringing a nun would envy.

Ed arrives, in his pink Cadillac car. He is 'in business'. Kath sends Kemp off to fetch Sloane's suitcase and Sloane goes for a lie-down. Ed has found out that Kath has "got a lad in". Kath explains that she met Sloane in the library, and that he was having problems with his rent. Kath has clearly done this sort of thing before and Ed tells her that Sloane must go. But when Ed sees Sloane for himself, he starts to change his mind. It appears that Kath's first lover - and the father of her child - was Ed's best friend, Tommy.

Ed and Sloane bond over mutual interests - the navy, the gym, sports, bodybuilding. Ed offers to make Sloane his chauffeur, complete with leather uniform, and warns him against Kath. Ed tells Kath that he will be paying for Sloane's board and lodging.

When Ed has gone, Kath puts on a negligee and invites Sloane into the lounge. She shows him some old photographs and tells him that he reminds her of Tommy. They have sex on the sofa, as Kath cries out that she will be so ashamed in the morning.

Sloane becomes well ensconced in the house, with both Kath and Ed competing for his affections. But he oversteps the mark, leaving the house at night, joyriding in Ed's car and doing some entertaining of his own in the back seat. Ed finds a lipstick in the car. Kemp breaks his twenty-year silence to tell Ed that he suspects Sloane of murdering his old boss, that Sloane has made Kath pregnant, and that Sloane has been tormenting him. Ed reacts angrily and confronts Sloane, who protests his innocence. Ed gives him another chance, telling him that women are something he will grow out of, with Ed's help. Ed has never forgiven Kath for sleeping with Tommy. He suggests that Sloane moves into his flat.

Sloane reprimands Kemp for telling tales. Kemp says he is going to the police. Sloane kicks him to death.

Ed is really annoyed now, but still Sloane begs forgiveness. Impressed by Sloane's sincerity, especially when he puts a hand on Ed's knee, Ed agrees to help. He explains to Kath that she must tell the doctor that the old man fell down the stairs, and tells her Sloane will be coming to live with him from now on. But Kath insists that she will go to the police if Sloane goes away with Ed, and confesses gleefully that she's pregnant. Ed says he'll go to the police if Sloane stays with Kath. Faced with this dilemma, Sloane hits out angrily at Kath, dislodging her dentures and breaking them.

A happy solution is found - Kath and Ed can share Sloane, six months at a time. Ed solemnises a marriage between Kath and Sloane, then Kath does the same for Ed and Sloane. Sloane is trapped.