Ash Flanders and Luke Mullins in Little Mercy.

Doting parents … Ash Flanders and Luke Mullins. Photo: Marco Del Grande

Mercy, goes the publicity, is a little eight-year-old girl with a taste for ice-cream and lollipops. Her parents, theatre director Roger Summers (Luke Mullins) and his glamorous alcoholic housewife Virginia (Ash Flanders in a sober skirt and nails), think Mercy can do no wrong.

That's no surprise given this couple is blind to Mercy's overt wrongness from the beginning. Indeed, everything is wrong here, deliberately so in this bent satirical take on the demonic child Hollywood movie phenomenon: think The Omen, The Exorcist or, going way back, The Bad Seed.

In Little Mercy, the child who miraculously arrives at the house of this previously childless couple is performed by Jill McKay, an actor who, it would be safe to say, hasn't been cast in a child role any time since the mid- 20th century - she's 76.

Melbourne theatrical duo Sisters Grimm - the creative pairing of Flanders and the play's director, Declan Greene - have rewritten and are now freshly staging Little Mercy for the Sydney Theatre Company three years after its first, very different production in a dodgy disused Melbourne car park.

Sisters Grimm usually stage plays that deliberately engage with ''found spaces'' - even if that space requires first spending hours moving out huge mounds of rubbish and taking it to the tip. What this little self-described ''queer D.I.Y theatre group'' will make of an actual theatre will be curious to see.

''Our last show, Summertime in the Garden of Eden, was staged in someone's backyard shed,'' says Flanders, having removed his wig and skirt as Virginia after Metro's photo shoot. ''The plot centred around a gorgeous plantation house in the old south and everyone was fighting for the house,'' he says.

''We usually point out the absurdity of the venue we're working in; here we've had to do something different, making a piece for the theatre, which we haven't done for a little while.''

Greene says the core ethos is to take a story and deliberately miscast everything about it: chiefly the actors and the venue. ''Our shows are always this big exercise in failure: desperately trying to achieve the effect of a certain genre - in this case the evil-child genre - but with resources that are completely inadequate or inappropriate.''

Melbourne theatre critic Alison Croggon has described Sisters Grimm's work as ''meta-theatrical camp'' with ''low-tech pleasures'', and that Little Mercy in its original incarnation was ''irresistibly funny nonsense'' delivered with ''brio and flair''.

Greene and Flanders met when they did an ''awful play together'' (unintentionally awful, they mean) at the Melbourne International Comedy Festival in 2005.

These days, they build their play in front of an audience, a process more akin to live music than to traditional theatre. Sound designer and musician Steve Toulmin scores the play live, making the experience almost like watching an old melodramatic silent film.

They're intrigued by the evil-kid phenomenon in movies; their ''queering'' of that genre takes the idea there's always a mother who understands intuitively that her child is evil, but no one believes her, and having a man play her role.

Part of the audience appeal for these movies was seeing wealthy people's lives implode, say the theatre-makers.

''We love seeing little kids misbehave,'' Greene says.

''There's something perversely great about watching a little kid have a tantrum in a grocery store because you think: man, I want to be that kid.''

LITTLE MERCY

Thursday, March 7 to Sunday, March 24. Tuesday 7pm, Wednesday and Thursday 8.15pm, Friday and Saturday 6.30pm and 9.30pm, Sunday 4pm. Wharf 2 Theatre, Hickson Road, Walsh Bay.

TICKETS sydneytheatre.com.au, 9250 1777, $25/$30.

TRAVEL A 20-minute walk from trains, ferries and buses at Circular Quay, street and undercover car parking nearby, taxis to the door.

SHOW Twisted take on the evil-child genre.

STARS Ash Flanders, Jill McKay and Luke Mullins.

DIRECTOR Declan Greene.