How is the whole thing maintained?

The play is VERY different, and, having seen Girly first, it stands as a testament to Brian Comport's creativity and imagination.

Off the bat, some of the stand-out differences:

The entirety of the play takes place in the living room of the house.

Nanny is much older-- 70 years old, according to the list of characters.

Other than Nanny, the costumes are also completely different. The script calls for Mumsy to spend the entirety of the play in a baggy bathrobe, and Girly and Sonny dress like mods-- frilly white shirts, a black suit for Sonny and a black skirt with suspenders for Girly (who also wears a panama hat). Both of them are chain smokers.

There are no snuff movies

There is no "Friend in Five" character

When they're onstage together, Sonny and Girly speak most of their lines in unison and really only have individual dialogue when one or the other is off stage

The "medicine" that everyone takes round the kitchen table is specified to be gin, and Mumsy and Nanny get hammered on it

Nanny disposes of bodies by burying them out in the garden (which can be seen through the living room window)

The first half of the play is about what happens when they bring home "Chick"-- who is sort of both Soldier and New Friend. He's a homeless 20-year-old, and the children have picked him up in the park. He's got the ill-manners of Soldier, but like New Friend starts to play along with the game once he recognizes the potential benefits (ie, Mumsy and Girly). Chick participates in "The Game" (which is a lot more innocuous and just kind of weird-- one scene opens with him wearing a paper crown and writing out "A Boy's best friend is his mumsy" over and again on ruled paper as though he's in detention) and there's no dead girlfriend to blackmail him with. It comes out that The Game originated when Daddy, who didn't want any more children, made Mumsy have a hysterectomy (called "having the major"), but then shortly thereafter abandoned her. Sonny plots against Chick, but not because he's upsetting the status quo; rather, Sonny is upset because he's bisexual and wants to get it on with Chick, who has no interest. Chick gets wise to Sonny's plotting and encourages Girly to kill him, which she does by pushing him off the banister (which, it's implied, Girly and Mumsy have done to previous "friends"). Chick then assumes the Sonny role, and he and Girly scout out a New Friend, an 18 year old named Doll-- as Chick wants to create a harem of sorts for himself. Doll, however, turns out to be a lesbian/bisexual (it's never specified which), and forms an attachment to Girly, and they begin speaking in unison. Doll starts to ponder knocking one of them off in order to maintain his newfound power. Before he can, though, Mumsy and Nanny get smashed on gin and Mumsy admits that she only really wanted children in the first place because of societal expectations. She and Nanny admit that they've been in love with one another for years and decide to start a new life together. The play ends with Mumsy and Nanny killing Girly, Chick, and Doll with poisoned berry sundaes; as they eat, Mumsy reads them a bedtime story while Nanny sinisterly enters the room carrying the shovel she's going to use to bury them in the garden. Girly, Chick, and Doll all fall over on the floor gagging and choking as Mumsy and Nanny cackle, and the curtain falls.