It started during rehearsals, when her co-star told her he had romantic feelings for her and said he wanted to touch her.
The harassment escalated once the play opened, with him forcefully shoving his tongue into her mouth during a kissing scene.
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Then, night after night, he would press his groin into her from behind while they were standing in the wings.
His behaviour left her panicking during performances and in dread of taking the stage each night.
The actress, who asked not to be named for legal reasons and for fear of it destroying her career, said she was sexually harassed both on stage and off by the actor.
Despite repeatedly reporting the matter to the play's director, who alerted senior staff at the theatre company, no effective action was taken to stop the harassment, she said. Fearing for her safety, she felt she had no option but to withdraw from the production.
When another actress was hired to replace her in the role, she said she was "devastated" to learn that the company had not told the woman why she had left the production, potentially putting her in danger.
'He said he wanted to touch me'
During rehearsals, her colleague told her he had "romantic feelings" towards her, she said. She told him that was "unprofessional and inappropriate".
While rehearsing a kissing scene, he told her it was difficult "to kiss me without wanting more". Again, she told him that was "unprofessional".
He then asked her if he could give her a massage. "He said he wanted to touch me." She said no.
She told the director about the man's behaviour. The director, a woman, asked the actress what she wanted her to do. The director suggested speaking to the man directly. The actress, worried that doing so might jeopardise the production, said no, and asked the director to instead keep an eye on things.
In the lead-up to opening night, the actor wrote her a lengthy poem expressing his feelings towards her. "I was overwhelmed and unsettled. I told him to stop."
Once the play opened, the harassment escalated, she said. "He began to extend an onstage kiss with me. It became noticeably long, so much so that an audience member commented. I was very uncomfortable."
Both actors were directed to shorten the kiss. He asked if she agreed with the instruction: she said yes. "That night on stage he grabbed my face and forcefully pushed his tongue far into my mouth ..."
"During each performance we were required to stand, briefly, in a small space alone backstage. I had to face the wall and he stood behind," she said.
He started "holding me by my hips and pushing himself up against me. I could feel the imprint of his penis. It was paralysing.
"I began to dread this moment each night. I would panic as this section of the performance approached. I ... panicked before and during any moments of performed intimacy.
"I felt unsafe both on and off stage."
'I was scared to provoke him'
The director asked the actress how she would like her to handle the matter. The director then informed the stage manager and fight choreographer.
The actress said she spoke again to the director when the harassment continued. The director asked if she wanted her to speak to the actor directly about the matter, but the actress feared his reaction.
"By now I was scared for her to do so. I didn't trust that he would have a reasonable response ... I was scared to provoke him."
Instead, the director said she would report the matter to a senior staff member. The staff member called the actress into a meeting a week later.
"She began the meeting smiling," the actress said, before commenting: "So I hear someone's got a bit of a crush on you". "I was shocked," she said. "I felt alone and unprotected."
The staff member said she could either speak to the actor or ask the stage manager to "keep an eye on things".
The actress said she chose the latter option because she did not trust the staff member and feared how the man would respond if he was reprimanded.
"I was expected to walk on stage with him and kiss him after he had been spoken to."
'No one knew what to do'
Her fears grew as the season progressed while she continued to complain to management. "Not one of them took any decisive action," she said. "I was becoming paralysed by fear and discomfort.
"What was clear was that no one knew what to do. There appeared to be no formal protocols or procedures that kicked in when I reported his behaviour. This left me in a dangerous situation. It also left my director, and stage managers, in an awful position. They wanted to protect me, but they didn't know how."
She started having panic attacks. "I was unable to sleep. I had abdominal pain and difficulty breathing."
She decided to quit the production, and notified senior staff at the theatre company, her agents, and a lawyer from Actors Equity in writing. Doing so, her lawyer advised, meant the company was legally required to investigate her case.
Several days later, the company contacted her lawyer, saying it "had investigated and found the male actor safe to continue in the role".
"My character was re-cast," she said. "I requested that my replacement ... be told why I left ... I found out a couple of days later that she wasn't. She had been told I was sick.
"I was devastated that another female actor had been put in a potentially dangerous situation. I contacted the stage managers and asked them to protect her. They told me they would. I could only hope that they could.
"I was paid out for the season. I found a psychologist and the company covered 18 sessions with him. I now continue to see him and cover the cost myself."