Murphy, whose Holding the Man was staged by Silo Theatre in 2009, makes 90-year-old Gwen the central character in a story about a family struggling with the "what to do about Mum?" question. Deciding Gwen is too old to live alone in the family home, they move her into a new house, filled with labour-saving gadgets, the first to be built in a new suburban wilderness.
A Catholic, Gwen calls a priest in to bless the house which heralds the arrival of Nigerian minister Father Ezekiel (Tawanda Manyimo), who must deal not only with Gwen's belief that the new house is a form of purgatory, but also her domineering son (Bruce Phillips), put-upon daughter (Michele Hine) and wayward grandson (Ryan Richards). All the while, Father Ezekiel is feeling isolated from his own family.
"It's very clever to have a character who is an African priest because it allows all sorts of issues, like the way we look after our elders in Western culture, to be examined," says Elizabeth. "No one seems to be looking after Gwen because they're all caught up with their own lives."
Katherine, who has directed Shortland Street, Go Girls and Nothing Trivial, believes the audience will empathise with the characters.
"The characters are symbolic of the plights we face at various ages and stages and you can see the situation from everyone's point of view and sympathise with each of them to a degree," she says.
She and Elizabeth weren't daunted by the prospect of working together on a play with the potential to provoke their own thoughts and feelings about family.
"We have a very good relationship to build on so it would take much more than this to rock it," says Elizabeth.
"We approach the work as two professionals; I respect her as a director and she respects me as an actor."
Katherine says she has wanted to direct her mother for years and, thanks to friends who brought the script back after seeing Gwen in Purgatory, has found the right project. "It's a beautiful script which exposes the strength and vulnerability of family. It resonated with us both."
Theatre preview
What: Gwen in Purgatory
Where and when: Tapac, Western Springs, September 11-29