The actress, who recently bowed out as Walford's Julie Perkins, will take on the role of crazed Annie Wilkes in an adaptation of Stephen King's classic novel, News Shopper reports.
Misery is being staged at Fairfield Halls in Croydon for a seven-show run next month.
Murphy left the cast of EastEnders in the summer after nearly a year playing Julie, who was Billy Mitchell's love interest.
The 44-year-old later explained that she was happy over her departure as it gave her the opportunity to pursue new parts.
She said at the time: "I think that's what I do - I love the fact that my job's always different. I've had loads of nice work in my years - I like playing lots of different parts. That's me and that's what I do. I like spicing it up with a bit of theatre here and a film there. I like the variety of it all."
Murphy appears in Misery between October 4 and October 8.
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