At The Mercury Theatre in London's West End, rumours are circulating of a curse. It is said that the lead actress Lilith has made a pact with Melpomene, the tragic muse of Greek mythology, to become the greatest actress to ever grace the stage. Suspicious of Lilith, the jealous wife of the theatre owner sends dresser Jenny to spy on her, and, desperate for the money to help her family, Jenny agrees.

What Jenny finds is a woman as astonishing in her performance as she is provocative in her nature. On stage, it's as though Lilith is possessed by the characters she plays, yet off stage she is as tragic as the muse who inspires her, and Jenny, sorry for her, befriends the troubled actress. But when strange events begin to take place around the theatre, Jenny wonders whether the rumours are true and fears that when the muse comes calling for payment, the cost will be too high.