The new stage play, adapted by author, journalist and broadcaster Rebecca Reid, follows Allie – a recently divorced mum, balancing being a single parent with the launch of her tech start-up.
When she decides to advertise for a lodger to help make ends meet, the delightful Hedy offers her a lifeline.
But as their lives intertwine, boundaries blur and a seemingly perfect arrangement begins to unravel with chilling consequences.
“Jennifer Jason Leigh was just incredible at playing Hedy [in the film] so they were big shoes to fill,” said Marsh.
The 49-year-old, who shot to fame in 2021 as a member of Hear’Say in the ITV reality show Popstars, added: “Thankfully I can play her slightly differently.”