Everyone (almost everyone, that is) has three plugs of three prongs each, either male or female. Whichever type of plug you have a majority of determines what sex you are considered to be. If one of your plugs matches someone elses, you can hook them up for shared pleasure. If more than one of your plugs matches, you can immediately get married by hooking both or all three of them up!
The hero of our story is a somewhat mousy little man who works at the zoo. One day on his way home he stumbles across his girlfriend getting raped--someone whose plugs dont match hers is trying to force a connection anyway. He summons all his courage and chases the bastard away. Oh Stu, the girl says, gasping her thanks. They fumble their appendages together and hook one plug pair together in hasty passion. Oh, Owa, Stu says. He reaches for her, seeking, touching. He finds another of her plugs with one of his.... It matches.... Lets just, lets just-- he says, pressing closer, closer, to plugging in. Get married right now? she says, scared, delighted. Their plugs slide closer, closer....